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vue系列---Mustache.js模板引擎介绍及源码解析(十)

2019-10-30 09:30 龙恩0707 阅读(...) 评论(...) 编辑 收藏

mustache.js(3.0.0版本) 是一个javascript前端模板引擎。官方文档(https://github.com/janl/mustache.js)

根据官方介绍:Mustache可以被用于html文件、配置文件、源代码等很多场景。它的运行得益于扩展一些标签在模板文件中,然后使用一个hash字典或对象对其进行替换渲染操作。

基本语法如下:

1. {{ keyName }}: 读取属性值, 如果有html标签的话,会被转义。
2. {{{ keyName }}}: 读取属性值且原样输出,即html不进行转义。
3. {{ #keyName }} {{ /keyName }}: 用于遍历。
4. {{ ^keyName }} {{ /keyName }}: 反义数据,当keyName不存在、或为null,或为false时会生效。可以理解相当于我们js中的 !(非)。
5. {{.}}: 用于遍历数组。
6. {{ !comments }}: 用于注释。
7. Partials: 使用可重用的模板,使用方式:{{> 变量}}。

1. 变量 {{ keyName }} 或 {{{ keyName }}}

标签最主要是通过一个变量来使用。比如 {{ keyName }}标签在模板中会尝试查找keyName这个变量在当前的上下文中,如果上下文中不存在keyName变量,那么它会通过递归的方式依次查找它的父级元素,依次类推... 如果最顶级的上下文中依然找不到的话,那么该keyName变量就不会被渲染。否则的话,keyName标签就会被渲染。
如果变量中存在html标签会被转义的。因此如果我们不想html标签转义的话,我们可以使用三个花括号 {{{ keyName }}}.

比如如下列子:
项目基本结构如下:

|--- mustache 文件夹
| |--- index.html
| |--- mustache.js (库文件)

基本代码如下所示:

<!DOCTYPE html>
<html>
<head>
  <title>mustache--demo</title>
  <meta charset="utf-8">
  <script type="text/javascript" src="./mustache.js"></script>
</head>
<body>
  <script type="text/javascript">
    var data = {
      "name": "<a>kongzhi<a>",
      "msg": {
        "sex": " male ", 
        "age": "31",
        "marriage": 'single'
      }
    }
    var tpl = '<p> {{name}}</p>'; 
    var html = Mustache.render(tpl, data); 
   console.log(html); // 打印如下:<p> &lt;a&gt;kongzhi&lt;a&gt;</p>
 </script>
</body>
</html>

如上可以看到,我们name字段,存在a标签中的 < 或 > 被转义了,如果我们想它们不需要转义的话,我们需要使用三个花括号 {{{}}}。如下代码输出:

<!DOCTYPE html>
<html>
<head>
  <title>mustache--demo</title>
  <meta charset="utf-8">
  <script type="text/javascript" src="./mustache.js"></script>
</head>
<body>
  <script type="text/javascript">
    var data = {
      "name": "<a>kongzhi<a>",
      "msg": {
        "sex": " male ", 
        "age": "31"
      }
    }
    var tpl = '<p> {{{name}}}</p>'; 
    var html = Mustache.render(tpl, data); 
   console.log(html); // 打印 <p> <a>kongzhi<a></p>
 </script>
</body>
</html>

当然如果我们上面不想使用三个花括号的话,我们也可以使用 & 告诉上下文不需要进行转义。比如 {{ &name }} 这样的,如上面的三个花括号 {{{ name }}}, 我们也可以改成 {{ &name }}; 效果是一样的。

2. 块

2.1 {{#keyName}} {{/keyName}}

{{#keyName}} 是一个标签,它的含义是块的意思。所谓块就是渲染一个区域的文本一次或多次。
块的开始形式是:{{#keyName}},结束形式是:{{/keyName}}。

我们可以使用该 {{#keyName}} {{/keyName}} 标签来遍历一个数组或对象。如下代码所示:

<!DOCTYPE html>
<html>
<head>
  <title>mustache--demo</title>
  <meta charset="utf-8">
  <script type="text/javascript" src="./mustache.js"></script>
</head>
<body>
  <script type="text/javascript">
    var data = {
      "name": "kongzhi",
      "msg": {
        "sex": " male ", 
        "age": "31",
        "marriage": 'single'
      }
    }
    var tpl = `{{ #msg }}<div>{{sex}}</div><div>{{age}}</div><div>{{marriage}}</div>{{ /msg }}`;
    var html = Mustache.render(tpl, data); 
   console.log(html); // 打印 <div> male </div><div>31</div><div>single</div>
 </script>
</body>
</html>

注意:如果上面的 msg 是一个布尔值 false的话,即 msg: false, 那么 tpl 模板不会被渲染。最后html为 ''; 但是如果 msg 的值是 msg: {} 这样的话,那么tpl会渲染,只是没有值而已,最后输出:'<div></div><div></div><div></div>' 这样的。

Function

当keyName的值是一个可以被调用的对象,或者是一个函数的话,那么该函数会被调用并且传递标签包含的文本进去。如下代码所示:

<!DOCTYPE html>
<html>
<head>
  <title>mustache--demo</title>
  <meta charset="utf-8">
  <script type="text/javascript" src="./mustache.js"></script>
</head>
<body>
  <script type="text/javascript">
    var data = {
      "name": "kongzhi",
      "msg": {
        "sex": " male ", 
        "age": "31",
        "marriage": 'single'
      },
      "wrapped": function() {
        return function(text, render) {
          return '<div>' + render(text) + '</div>'
        } 
      }
    }
    var tpl = `{{#wrapped}} {{name}} is men {{/wrapped}}`;
    var html = Mustache.render(tpl, data); 
   console.log(html); // 打印 <div> kongzhi is men </div>
 </script>
</body>
</html>

如果该变量的值也是一个函数的话,那么我们也可以迭代上下文的数组。如下代码演示:

<!DOCTYPE html>
<html>
<head>
  <title>mustache--demo</title>
  <meta charset="utf-8">
  <script type="text/javascript" src="./mustache.js"></script>
</head>
<body>
  <script type="text/javascript">
    var data = {
      "msg": [
        { 'firstName': 'kongzhi111', "lastName": 'kong' },
        { 'firstName': 'kongzhi222', "lastName": 'zhi' }
      ],
      "name": function() {
        return this.firstName + " " + this.lastName;
      }
    }
    var tpl = `{{#msg}} {{name}} {{/msg}}`;
    var html = Mustache.render(tpl, data); 
   console.log(html); // 打印 kongzhi111 kong  kongzhi222 zhi 
 </script>
</body>
</html>

2.2 {{ ^keyName }} {{ /keyName }}

{{ ^keyName }} {{ /keyName }} 的含义是:取相反的数据。当keyName不存在、或为null,或为false时会生效。可以理解相当于我们js中的 !(非) 如下代码所示:

<!DOCTYPE html>
<html>
<head>
  <title>mustache--demo</title>
  <meta charset="utf-8">
  <script type="text/javascript" src="./mustache.js"></script>
</head>
<body>
  <script type="text/javascript">
    var data = {
      "name": "kongzhi",
      "msg": null // 为null, undefined, '' 或 false,数据才会被渲染
    }
    var tpl = `{{ ^msg }}<div>暂无数据</div>{{ /msg }}`;
    var html = Mustache.render(tpl, data); 
   console.log(html); // 打印 <div>暂无数据</div>
 </script>
</body>
</html>

2.3 {{.}}

{{.}} 也是可以遍历一个数组。

如下代码:

<!DOCTYPE html>
<html>
<head>
  <title>mustache--demo</title>
  <meta charset="utf-8">
  <script type="text/javascript" src="./mustache.js"></script>
</head>
<body>
  <script type="text/javascript">
    var data = {
      "name": "kongzhi",
      "msg": ['111', '222', '333']
    }
    var tpl = `{{#msg}} {{.}} * {{/msg}}`;
    var html = Mustache.render(tpl, data); 
   console.log(html); // 打印 111 *  222 *  333 * 
 </script>
</body>
</html>

3. {{ !comments }}

{{ !comments }} 可以理解为代码注释。良好的编码习惯,都会有一些注释来辅佐。同样在我们的 mustache中也存在注释的标签。
下面我们来看看如何使用注释:

如下代码:

<!DOCTYPE html>
<html>
<head>
  <title>mustache--demo</title>
  <meta charset="utf-8">
  <script type="text/javascript" src="./mustache.js"></script>
</head>
<body>
  <script type="text/javascript">
    var data = {
      "name": 'kongzhi'
    }
    var tpl = `<div>{{name}}</div>{{ ! 这是一段注释 }}`;
    var html = Mustache.render(tpl, data); 
   console.log(html); // 打印 <div>kongzhi</div> 
 </script>
</body>
</html>

4. Partials的使用

Partials的含义是:使用可重用的模板,使用方式:{{> 变量}}. 相当于 include 的意思。

可以查看如下demo演示:

<!DOCTYPE html>
<html>
<head>
  <title>mustache--demo</title>
  <meta charset="utf-8">
  <script type="text/javascript" src="./mustache.js"></script>
</head>
<body>
  <script type="text/javascript">
    var data = {
      "name": "kongzhi",
      "msg": ['111']
    }
    var tpl = `{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}`;
    var html = Mustache.render(tpl, data); 
   console.log(html); // 打印 111 * <div>kongzhi</div>  
    /*
     * 如上我们的tpl模板文件中引入了 <div>{{name}}</div> 模块,但是该模块在其他的地方
     * 也使用到了,因此我们想让他当做一个模板定义,在需要的地方 引用进来。因此我们如下这样做了:
     var data = {
        "name": "kongzhi",
        "msg": ['111']
     }
     var temp = `<div>{{name}}</div>`;
     var tpl = `{{#msg}} {{.}} * {{> user }} {{/msg}}`;
     var html = Mustache.render(tpl, data, {
       user: temp
     }); 
     console.log(html); // 打印 111 * <div>kongzhi</div> 
    */ 
 </script>
</body>
</html>

5. 设置分割符号

有些时候我们想修改一下 mustache默认的标签分割符号 {{}}. mustache也允许我们这样做的。并且修改的方法很简单。
比如说我们把分隔符改成 {% %} 这样的 ,或者 {{% %}}这样的,也是可以的。我们只需要 Mustache.render 方法中传递第四个参数,并且模板也需要改成这样的分割符号,如下代码所示:

<!DOCTYPE html>
<html>
<head>
  <title>mustache--demo</title>
  <meta charset="utf-8">
  <script type="text/javascript" src="./mustache.js"></script>
</head>
<body>
  <script type="text/javascript">
    console.log(Mustache);
    var data = {
      "name": "kongzhi",
      "msg": ['111']
    }
    var tpl = `{{%#msg%}} {{%.%}} * <div>{{%name%}}</div> {{%/msg%}}`;
    var html = Mustache.render(tpl, data, {}, [ '{{%', '%}}' ]); 
   console.log(html); // 打印 111 * <div>kongzhi</div>  
 </script>
</body>
</html>

如上可以看到,我们在 Mustache.render 方法中,传递了第四个参数为 [ '{{%', '%}}' ],因此在模板中我们的开始标签需要使用 '{{%'这样的,在结束标签使用 '%}}' 这样的即可。或者改成任何其他自己喜欢的分隔符都可以,关键设置第四个参数和模板要对应起来。

二:Mustache.js 源码分析

我们首先引入 mustache库文件后,然后我们在页面上打印 console.log(Mustache); 看到打印如下信息:

{
  Context: fn(view, parentContext),
  Scanner: fn,
  Writer: fn,
  clearCache: fn,
  escape: function escapeHtml(){},
  name: "mustache.js",
  parse: fn(template, tags),
  render: fn(template, view, partials, tags),
  tags: ["{{", "}}"],
  to_html: fn(template, view, partials, send),
  version: "3.0.0"
}

如上我们可以看到我们的 Mustache.js 库对外提供了很多方法。下面我们来分析下源码:

1. 入口结构如下:

(function defineMustache (global, factory) {
  /*
   如下判断支持 CommonJS 规范引入文件 或 AMD 规范引入文件,或直接引入js文件,
   Mustache 就是我们的全局变量对外暴露。
  */
  if (typeof exports === 'object' && exports && typeof exports.nodeName !== 'string') {
    factory(exports); // CommonJS
  } else if (typeof define === 'function' && define.amd) {
    define(['exports'], factory); // AMD
  } else {
    global.Mustache = {};
    factory(global.Mustache); // script, wsh, asp
  }
}(this, function mustacheFactory(mustache) {
  
  var objectToString = Object.prototype.toString;
  /*
   * 判断是否是一个数组的方法
  */
  var isArray = Array.isArray || function isArrayPolyfill (object) {
    return objectToString.call(object) === '[object Array]';
  };
  // 对象是否是一个函数
  function isFunction (object) {
    return typeof object === 'function';
  }
  // 判断类型
  function typeStr (obj) {
    return isArray(obj) ? 'array' : typeof obj;
  }
  function escapeRegExp (string) {
    return string.replace(/[\-\[\]{}()*+?.,\\\^$|#\s]/g, '\\$&');
  }
  // 判断对象是否有该属性
  function hasProperty (obj, propName) {
    return obj != null && typeof obj === 'object' && (propName in obj);
  }
  // 判断原型上是否有该属性
  function primitiveHasOwnProperty (primitive, propName) {  
    return (
      primitive != null
      && typeof primitive !== 'object'
      && primitive.hasOwnProperty
      && primitive.hasOwnProperty(propName)
    );
  }
  // Workaround for https://issues.apache.org/jira/browse/COUCHDB-577
  // See https://github.com/janl/mustache.js/issues/189
  var regExpTest = RegExp.prototype.test;
  function testRegExp (re, string) {
    return regExpTest.call(re, string);
  }

  var nonSpaceRe = /\S/;
  function isWhitespace (string) {
    return !testRegExp(nonSpaceRe, string);
  }
  // 对< > 等进行转义
  var entityMap = {
    '&': '&amp;',
    '<': '&lt;',
    '>': '&gt;',
    '"': '&quot;',
    "'": '&#39;',
    '/': '&#x2F;',
    '`': '&#x60;',
    '=': '&#x3D;'
  };
  // 转换html标签进行转义操作
  function escapeHtml (string) {
    return String(string).replace(/[&<>"'`=\/]/g, function fromEntityMap (s) {
      return entityMap[s];
    });
  }

  var whiteRe = /\s*/;   // 匹配0个或多个空白
  var spaceRe = /\s+/;   // 匹配至少1个或多个空白
  var equalsRe = /\s*=/; // 匹配字符串 "=",且前面允许0个或多个空白符,比如 "=" 或 "  =" 这样的。
  var curlyRe = /\s*\}/; // 匹配 "}" 或 " }" 
  var tagRe = /#|\^|\/|>|\{|&|=|!/; // 匹配 '#', '^' , '/' , '>' , { , & , = , ! 任何一个字符 
  // ...... 代码略
  mustache.name = 'mustache.js';
  mustache.version = '3.0.0';
  mustache.tags = [ '{{', '}}' ];
  // ..... 代码略
  mustache.escape = escapeHtml;

  // Export these mainly for testing, but also for advanced usage.
  mustache.Scanner = Scanner;
  mustache.Context = Context;
  mustache.Writer = Writer;
  mustache.clearCache = function clearCache () {};
  mustache.parse = function parse (template, tags) {};
  mustache.render = function render (template, view, partials, tags) {};
  mustache.to_html = function to_html (template, view, partials, send) {};
}));

如上代码内部的一些工具函数,稍微了解下就好。及把很多函数挂载到 mustache对外暴露的对象上。因此我们上面打印 console.log(Mustache);  就可以看到 该对象下有很多方法和属性,如上就是对外暴露的。

下面我们可以根据demo来分析,如下demo代码:

var data = {
  "name": "kongzhi",
  "msg": ['111']
}
var tpl = `{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}`;
var html = Mustache.render(tpl, data); 
console.log(html); // 打印 111 * <div>kongzhi</div> 

从上面我们打印的 console.log(Mustache) 可知:该全局变量有很多方法,其中就有一个 render方法,该方法接收4个参数,如下代码:Mustache.render(tpl, data, ,partials, tags); 各个参数含义分别如下:tpl(模板),data(模板数据),partials(可重用的模板), tags(可自定义设置分隔符);

如上我们只传入两个参数,其中 tpl 是必须传递的参数,否则不传会报错。因此会调用内部 render() 方法,方法代码如下所示:

mustache.render = function render (template, view, partials, tags) {
  if (typeof template !== 'string') {
    throw new TypeError('Invalid template! Template should be a "string" ' +
                        'but "' + typeStr(template) + '" was given as the first ' +
                        'argument for mustache#render(template, view, partials)');
  }

  return defaultWriter.render(template, view, partials, tags);
};

然后返回 defaultWriter.render(template, view, partials, tags); 函数,defaultWriter 是 Writer方法的实列,因此它有Writer对象中所有的属性和方法。从源码中如下代码可知:

var defaultWriter = new Writer();

Write 函数原型上有如下方法:

function Writer () {
  this.cache = {};
}
Writer.prototype.clearCache = function clearCache () {
  this.cache = {};
};
Writer.prototype.parse = function parse (template, tags) {
  // ...
};
Writer.prototype.render = function render (template, view, partials, tags) {
  // ...
}
Writer.prototype.renderTokens = function renderTokens (tokens, context, partials, originalTemplate) {
  // ...
}
Writer.prototype.renderSection = function renderSection (token, context, partials, originalTemplate) {
  // ...
}
Writer.prototype.renderInverted = function renderInverted (token, context, partials, originalTemplate) {
  // ...
}
Writer.prototype.renderPartial = function renderPartial (token, context, partials) {
  // ...
}
Writer.prototype.unescapedValue = function unescapedValue (token, context) {
  // ...
}
Writer.prototype.escapedValue = function escapedValue (token, context) {
  // ...
}
Writer.prototype.rawValue = function rawValue (token) {
  // ...
}

下面我们最主要看 Writer.prototype.render 中的方法吧,代码如下所示:

/*
 @param {template} 值为:"{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}";
 @param {view} 值为:{name: 'kongzhi', msg: ['111']}
*/
Writer.prototype.render = function render (template, view, partials, tags) {
  var tokens = this.parse(template, tags);
  var context = (view instanceof Context) ? view : new Context(view);
  return this.renderTokens(tokens, context, partials, template);
};

如上代码,我们首先会调用 this.parse(template, tags); 方法来解析该模板代码; 那么我们就继续看 parse 代码如下:

/*
 @param {template} 值为:"{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}";
 @param {tags} 值为:undefined
*/
Writer.prototype.parse = function parse (template, tags) {
  var cache = this.cache;
  /*
   template = "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}";
   tags的默认值:从源码可以看到:mustache.tags = [ '{{', '}}' ]; 因此:[ '{{', '}}' ].join(':') = "{{:}}"; 
   因此:cacheKey的值返回 "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}:{{:}}"
  */
  var cacheKey = template + ':' + (tags || mustache.tags).join(':');

  // 第一次 cache 为 {}; 所以 第一次 tokens 返回undefined; 
  var tokens = cache[cacheKey];

  /* 
    因此会进入 if语句内部,然后会调用 parseTemplate 模板进行解析,解析完成后,把结果返回 tokens = cache[cacheKey];
  */
  if (tokens == null)
    tokens = cache[cacheKey] = parseTemplate(template, tags);
  // 最后把token的值返回
  return tokens;
};

如上代码解析,我们来看下 parseTemplate 函数代码如下:

/*
 @param {template} 的值为:"{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}";
 @param {tags} 的值为:undefined
*/
function parseTemplate (template, tags) {
  // 没有模板,直接返回 [];
  if (!template)
    return [];
  var sections = [];     
  var tokens = [];       
  var spaces = [];       
  var hasTag = false;    
  var nonSpace = false;  
  // Strips all whitespace tokens array for the current line
  // if there was a {{#tag}} on it and otherwise only space.
  function stripSpace () {
    if (hasTag && !nonSpace) {
      while (spaces.length)
        delete tokens[spaces.pop()];
    } else {
      spaces = [];
    }

    hasTag = false;
    nonSpace = false;
  }
  var openingTagRe, closingTagRe, closingCurlyRe;
  function compileTags (tagsToCompile) {
    if (typeof tagsToCompile === 'string')
      tagsToCompile = tagsToCompile.split(spaceRe, 2);

    if (!isArray(tagsToCompile) || tagsToCompile.length !== 2)
      throw new Error('Invalid tags: ' + tagsToCompile);

    openingTagRe = new RegExp(escapeRegExp(tagsToCompile[0]) + '\\s*');
    closingTagRe = new RegExp('\\s*' + escapeRegExp(tagsToCompile[1]));
    closingCurlyRe = new RegExp('\\s*' + escapeRegExp('}' + tagsToCompile[1]));
  }
  compileTags(tags || mustache.tags);
  var scanner = new Scanner(template);
  var start, type, value, chr, token, openSection;
  while (!scanner.eos()) {
    start = scanner.pos;
    value = scanner.scanUntil(openingTagRe);

    if (value) {
      for (var i = 0, valueLength = value.length; i < valueLength; ++i) {
        chr = value.charAt(i);
        if (isWhitespace(chr)) {
          spaces.push(tokens.length);
        } else {
          nonSpace = true;
        }
        tokens.push([ 'text', chr, start, start + 1 ]);
        start += 1;
        // Check for whitespace on the current line.
        if (chr === '\n')
          stripSpace();
      }
    }

    // Match the opening tag.
    if (!scanner.scan(openingTagRe))
      break;

    hasTag = true;

    // Get the tag type.
    type = scanner.scan(tagRe) || 'name';
    scanner.scan(whiteRe);

    // Get the tag value.
    if (type === '=') {
      value = scanner.scanUntil(equalsRe);
      scanner.scan(equalsRe);
      scanner.scanUntil(closingTagRe);
    } else if (type === '{') {
      value = scanner.scanUntil(closingCurlyRe);
      scanner.scan(curlyRe);
      scanner.scanUntil(closingTagRe);
      type = '&';
    } else {
      value = scanner.scanUntil(closingTagRe);
    }

    // Match the closing tag.
    if (!scanner.scan(closingTagRe))
      throw new Error('Unclosed tag at ' + scanner.pos);

    token = [ type, value, start, scanner.pos ];
    tokens.push(token);

    if (type === '#' || type === '^') {
      sections.push(token);
    } else if (type === '/') {
      // Check section nesting.
      openSection = sections.pop();

      if (!openSection)
        throw new Error('Unopened section "' + value + '" at ' + start);

      if (openSection[1] !== value)
        throw new Error('Unclosed section "' + openSection[1] + '" at ' + start);
    } else if (type === 'name' || type === '{' || type === '&') {
      nonSpace = true;
    } else if (type === '=') {
      // Set the tags for the next time around.
      compileTags(value);
    }
  }
  // Make sure there are no open sections when we're done.
  openSection = sections.pop();

  if (openSection)
    throw new Error('Unclosed section "' + openSection[1] + '" at ' + scanner.pos);
  return nestTokens(squashTokens(tokens));
}

如上是 parseTemplate 源码,首先会进入 parseTemplate 函数内部,代码依次往下看,我们会看到首先会调用compileTags函数, 该函数有一个参数 tagsToCompile。从源码上下文中可以看到 mustache.tags 默认值为:[ '{{', '}}' ]; 因此 tagsToCompile = [ '{{', '}}' ]; 如果 tagsToCompile 是字符串的话,就执行 tagsToCompile = tagsToCompile.split(spaceRe, 2); 这句代码。

注意:其实我觉得这边 typeof tagsToCompile === 'string' 不可能会是字符串,如果是字符串的话,那么在 parse 函数内部就会直接报错了,如下代码内部:

Writer.prototype.parse = function parse (template, tags) {
  var cache = this.cache;
  var cacheKey = template + ':' + (tags || mustache.tags).join(':');
} 

如上,如果tags 传值了的话,它一定是一个数组,如果是字符串的话,那么使用 join分隔符会报错的。
如果 tagsToCompile 不是一个数组 或 它的长度 不等于2的话,那么就抛出一个错误。因为开始标签和结束标签必须成对传递。

继续往下看代码:openingTagRe = new RegExp(escapeRegExp(tagsToCompile[0]) + '\\s*');

如上代码,首先会调用 escapeRegExp 函数,传递了一个参数 tagsToCompile[0],从上面分析我们知道 tagsToCompile = [ '{{', '}}' ]; 因此 tagsToCompile[0] = '{{'了。escapeRegExp 函数代码如下:

function escapeRegExp (string) {
  // $& 的含义是:与 regexp 相匹配的子串。
  return string.replace(/[\-\[\]{}()*+?.,\\\^$|#\s]/g, '\\$&');
}

因此 代码实际就返回了这样的了 

return '{{'.replace(/[\-\[\]{}()*+?.,\\\^$|#\s]/g, '\\$&'); 

$& 含义是 与 regexp 相匹配的子串;那么匹配了被替换的结果就是 "\{\{";

因为 它匹配到 "{{", 匹配到第一个 "{" 的话,结果被替换为 "\{", 同理匹配到第二个的时候 也是 '\{'; 因此结果就是:"\{\{"; 也可以理解对 { 进行字符串转义。
因此 openingTagRe = new RegExp("\{\{" + '\\s*') = /\{\{\s*/;   接着往下执行代码:closingTagRe = new RegExp('\\s*' + escapeRegExp(tagsToCompile[1]));
tagsToCompile[1] 值为 "}}"; 同理 escapeRegExp(tagsToCompile[1]) 结果就变为:"\}\}";  因此 closingTagRe = new RegExp("\\s*" + "\}\}") = /\s*\}\}/;

从上面我们可知:openingTagRe 的含义可以理解为 开始标签,因此正则为 /\{\{\s*/ 就是匹配 开始标签 "{{ " 或 "{{",后面允许0个或多个空白。因为我们编写html模板的时候会这样写 {{ xxx }} 这样的。 因此 openingTagRe = /\{\{\s*/;  同理可知:closingTagRe 就是闭合标签了,因此正则需要为 /\s*\}\}/; 那么可以匹配结束标签 " }}" 或 "}}" 这样的了。因此 closingTagRe = /\s*\}\}/;

继续往下执行代码:

closingCurlyRe = new RegExp('\\s*' + escapeRegExp('}' + tagsToCompile[1]));

closingCurlyRe = new RegExp('\\s*' + escapeRegExp('}' + "}}")) = /\s*\}\}\}/; 该closingCurlyRe是匹配 " }}}" 或 "}}}" 这样的。

继续往下看代码:var scanner = new Scanner(template);

如上代码,会实列化 Scanner 函数,该函数会传递一个 template参数进去,template参数的值为:"{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"; 下面我们来看下 Scanner 函数源码如下:

function Scanner (string) {
  this.string = string;
  this.tail = string;
  this.pos = 0;
};

因此可以分别得出如下值:

this.string 值为:"{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"; 
this.tail 的值为:"{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"; 
this.pos = 0;
因此 scanner 实例化的值为 = {
    string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
    tail: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
    pos: 0
  };

继续看代码:var start, type, value, chr, token, openSection; 这些变量我们先不管他,然后继续代码往下:

然后就进入了while循环代码了,while (!scanner.eos()) {} 这样的。

eos方法如下所示:该方法的作用就是判断 scanner对象的 tail属性值是否等于空,如果等于空,说明模板数据已经被解析完成了。
如果解析完成了,就跳出while循环。如下代码:

Scanner.prototype.eos = function eos () {
  return this.tail === '';
};

第一次调用 scanner.eos(); 结果返回 false; 因此进入 while循环内部,start = scanner.pos = 0;

1. 第一次while循环

代码初始化调用 value = scanner.scanUntil(openingTagRe); openingTagRe 值为 /\{\{\s*/;  scanUntil函数代码如下:

Scanner.prototype.scanUntil = function scanUntil (re) {
  var index = this.tail.search(re), match;
  switch (index) {
    case -1:
      match = this.tail;
      this.tail = '';
      break;
    case 0:
      match = '';
      break;
    default:
      match = this.tail.substring(0, index);
      this.tail = this.tail.substring(index);
  }
  this.pos += match.length;
  return match;
};

如上 Scanner.prototype.scanUntil 函数代码可以看到,这里的this指向了 scanner 对象,因此 this.tail = "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"; 
re = /\{\{\s*/;  因此 var index = this.tail.search(re) = 0; 会进入 case 0: 的情况,因此 match = '';  最后 this.pos += ''.length = this.pos + 0 = 0; 最后返回 match = ''; 因此 value = '';  因此不会进入下面的 if(value){} 的语句里面,

scanner 此时值为:= {
   pos: 0,
   string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
   tail: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
}

继续往下代码执行 if (!scanner.scan(openingTagRe)) openingTagRe的值 = /\{\{\s*/; 函数如下:

Scanner.prototype.scan = function scan (re) {
 var match = this.tail.match(re);
 if (!match || match.index !== 0)
   return '';
 var string = match[0];
 this.tail = this.tail.substring(string.length);
 this.pos += string.length;
 return string;
};

1. if (!scanner.scan(openingTagRe)) {} 调用的时候,openingTagRe 值为 /\{\{\s*/; 因此re的值为 /\{\{\s*/ 此时 this.tail 值为 "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",re的值为:/\{\{\s*/;
var match = "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}".match(/\{\{\s*/); 因此:

match = [
     "{{", 
     index: 0, 
     groups: undefined, 
     input: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
];

因此 var string = match[0]; 即:string = "{{"; this.tail = this.tail.substring(string.length); this.tail = "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}".substring(2); 最后 this.tail = "#msg}} {{.}} * <div>{{name}}</div> {{/msg}}";
this.pos += "{{".length = 2; 返回 return string; 最后返回 "{{";

此时 scanner 的值为 = {
      pos: 2,
      tail: "#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
};

继续代码往下执行,看第二点解释:

2. 在parseTemplate函数中的 type = scanner.scan(tagRe) || 'name'; 这个代码调用的时候;  此时:this.tail的值为 = "#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"; tagRe 在页面初始化值为 = /#|\^|\/|>|\{|&|=|!/; 因此 re = /#|\^|\/|>|\{|&|=|!/; 因此 var match = this.tail.match(re) = "#msg}} {{.}} * <div>{{name}}</div> {{/msg}}".match(/#|\^|\/|>|\{|&|=|!/); 
即match的值为如下:

var match = [
     "#",
     index: 0,
     groups: undefined,
     input: "#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
];

因此 var string = match[0]; 即:string = '#'; this.tail = this.tail.substring(string.length);  this.tail = "#msg}} {{.}} * <div>{{name}}</div> {{/msg}}".substring(1);
最后 this.tail = "msg}} {{.}} * <div>{{name}}</div> {{/msg}}";  this.pos += "#".length = 3; 返回 return string; 最后返回 '#';
最后返回 type 的值为 "#";  此时的 scanner 的值为:

scanner = {
     pos: 3,
     tail: "msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
     string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
}

代码继续往下执行,看下面第三点解释:

3. 在 parseTemplate函数中的 scanner.scan(whiteRe); 中调用。 whiteRe 在页面初始化的正则为:var whiteRe = /\s*/;
从上面第二次调用的返回结果来看scanner的值为:

scanner的值为:= {
    pos: 3,
    tail: "msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
     string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
};

此时:this.tail 的值为 = "msg}} {{.}} * <div>{{name}}</div> {{/msg}}"; re = /\s*/;

Scanner.prototype.scan 函数源码如下(方便查看源码):

Scanner.prototype.scan = function scan (re) {
       var match = this.tail.match(re);
       if (!match || match.index !== 0)
         return '';
       var string = match[0];
       this.tail = this.tail.substring(string.length);
       this.pos += string.length;
       return string;
 };

因此 match = "msg}} {{.}} * <div>{{name}}</div> {{/msg}}".match(/\s*/);

var match = [
        "",
        index: 0,
        group: undefined,
        input: "msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
 ];

因此 var string = match[0]; 即:string = "";  this.tail = this.tail.substring(0) = "msg}} {{.}} * <div>{{name}}</div> {{/msg}}";
this.pos += 0; this.pos = 3; 返回 return string; 最后返回 "";
此时的 scanner 的值为:

scanner = {
        pos: 3,
        tail: "msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
        string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
 };

由上面我们知道 type = "#"; 因此会直接跳到 else 代码内部。

if (type === '=') {
        value = scanner.scanUntil(equalsRe);
        scanner.scan(equalsRe);
        scanner.scanUntil(closingTagRe);
} else if (type === '{') {
        value = scanner.scanUntil(closingCurlyRe);
        scanner.scan(curlyRe);
        scanner.scanUntil(closingTagRe);
        type = '&';
} else {
        value = scanner.scanUntil(closingTagRe);
}

因此 value = scanner.scanUntil(closingTagRe); 执行,看如下代码解释:
函数代码如下:

Scanner.prototype.scanUntil = function scanUntil (re) {
        var index = this.tail.search(re), match;
        switch (index) {
          case -1:
            match = this.tail;
            this.tail = '';
            break;
          case 0:
            match = '';
            break;
          default:
            match = this.tail.substring(0, index);
            this.tail = this.tail.substring(index);
        }
        this.pos += match.length;
        return match;
 };

scanner.scanUntil(closingTagRe);调用的时候;closingTagRe = "/\s*\}\}/";
因此 re = "/\s*\}\}/"; 从上面分析我们可以知道,最终 scanner 对象返回的值如下:

scanner = {
        pos: 3,
        string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
        tail: "msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
};

因此 此时的 var index = this.tail.search(re) = "msg}} {{.}} * <div>{{name}}</div> {{/msg}}".search(/\s*\}\}/) = 3;
因此会进入 default 的情况下;match = this.tail.substring(0, index);  match = "msg}} {{.}} * <div>{{name}}</div> {{/msg}}".substring(0, 3); = "msg";
因此 this.tail = this.tail.substring(index);  this.tail = "msg}} {{.}} * <div>{{name}}</div> {{/msg}}".substring(3);
最后 this.tail 的值为 = "}} {{.}} * <div>{{name}}</div> {{/msg}}";  this.pos += match.length; 因此 this.pos = 3 + 3 = 6; 
最后返回 match; 因此最后就返回 "msg" 字符串了。
此时我们再看下 scanner 的值为如下:

scanner = {
        pos: 6,
        string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
        tail: "}} {{.}} * <div>{{name}}</div> {{/msg}}"
 };

4. 在 parseTemplate 函数 内部中 if (!scanner.scan(closingTagRe)) 这句代码时候调用。
此时 scanner 的值如下所示:

scanner = {
         pos: 6,
         string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
         tail: "}} {{.}} * <div>{{name}}</div> {{/msg}}"
};
closingTagRe = "/\s*\}\}/";

Scanner.prototype.scan 函数源码如下(方便查看源码):

Scanner.prototype.scan = function scan (re) {
         var match = this.tail.match(re);
         if (!match || match.index !== 0)
           return '';
         var string = match[0];
         this.tail = this.tail.substring(string.length);
         this.pos += string.length;
         return string;
};

此时 this.tail 的值为 = "}} {{.}} * <div>{{name}}</div> {{/msg}}"; re = /\s*\}\}/;
var match = "}} {{.}} * <div>{{name}}</div> {{/msg}}".match(/\s*\}\}/);

var match = {
         "}}",
         groups: undefined,
         index: 0,
         input: "}} {{.}} * <div>{{name}}</div> {{/msg}}"
};
var string = match[0] = "}}";
this.tail = this.tail.substring(string.length);

因此 this.tail = "}} {{.}} * <div>{{name}}</div> {{/msg}}".substring(2);
最后 this.tail = " {{.}} * <div>{{name}}</div> {{/msg}}";
this.pos += "}}".length = 8;
最后返回 "}}"; 因此此时的 scannel 的值变为如下:

scanner = {
         pos: 8,
         string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
         tail: " {{.}} * <div>{{name}}</div> {{/msg}}"
 };

代码继续往下执行, 如下代码:

token = [ type, value, start, scanner.pos ];
tokens.push(token);
if (type === '#' || type === '^') {
    sections.push(token);
 } else if (type === '/') {
         // ...
 } else if (type === 'name' || type === '{' || type === '&') { 
      nonSpace = true;
 } else if (type === '=') {
      // Set the tags for the next time around.
      compileTags(value);
 }

因此 token = ["#", "msg", 0, 8]; tokens = [["#", "msg", 0, 8]];
因为 type = "#", 因此进入第一个if循环内部。因此 sections = [["#", "msg", 0, 8]];

2. 第二次while循环
此时的 scannel 的值为如下:

scanner = {
       pos: 8,
       string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
       tail: " {{.}} * <div>{{name}}</div> {{/msg}}"
 };

因此 start = 8;
继续执行如下代码:

value = scanner.scanUntil(openingTagRe); 
scanUtil 源码函数如下(为了方便理解,继续贴下代码)
Scanner.prototype.scanUntil = function scanUntil (re) {
        var index = this.tail.search(re), match;
        switch (index) {
          case -1:
            match = this.tail;
            this.tail = '';
            break;
          case 0:
            match = '';
            break;
          default:
            match = this.tail.substring(0, index);
            this.tail = this.tail.substring(index);
        }
        this.pos += match.length;
        return match;
 };

openingTagRe的值为:openingTagRe = /\{\{\s*/; 因此 re = /\{\{\s*/;  执行代码:var index = this.tail.search(re), match;
由上返回的数据可知:this.tail = " {{.}} * <div>{{name}}</div> {{/msg}}";   因此 var index = " {{.}} * <div>{{name}}</div> {{/msg}}".search(/\{\{\s*/) = 1;
同理进入default语句内部,因此 match = this.tail.substring(0, index);
match = " {{.}} * <div>{{name}}</div> {{/msg}}".substring(0, 1) = " ";
this.tail = this.tail.substring(index);
this.tail = " {{.}} * <div>{{name}}</div> {{/msg}}".substring(1);
最后 this.tail = "{{.}} * <div>{{name}}</div> {{/msg}}";
this.pos += match.length;
this.pos = 8 + 1 = 9;
最后返回 return match; 返回 " ";
因此 此时 scanner 的值变为如下:

scanner = {
   pos: 9,
   string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
   tail: "{{.}} * <div>{{name}}</div> {{/msg}}"
 };

执行完成后,value 此时的值为 " "; 因此会进入 if (value) {} 的内部代码。

注意:if("") {} 和 if (" ") {} 结果是不一样的。 "".length = 0; " ".length = 1; 源码如下(方便代码理解):

var regExpTest = RegExp.prototype.test;
     function testRegExp (re, string) {
       return regExpTest.call(re, string);
     }
     var nonSpaceRe = /\S/; // 匹配非空白字符
     function isWhitespace (string) {
       return !testRegExp(nonSpaceRe, string);
     }
     if (value) {
      for (var i = 0, valueLength = value.length; i < valueLength; ++i) {
        chr = value.charAt(i);

        if (isWhitespace(chr)) {
          spaces.push(tokens.length);
        } else {
          nonSpace = true;
        }

        tokens.push([ 'text', chr, start, start + 1 ]);
        start += 1;

        // Check for whitespace on the current line.
        if (chr === '\n')
          stripSpace();
      }
    }

因此 chr = ' '; 调用 isWhitespace(chr); 方法,其实就是调用了 RegExp.prototype.test.call(/\S/, ' '); 判断 ' ' 是否是非空白字符,因此返回false,在 isWhitespace 函数内部,使用了 !符号,因此最后返回true。
spaces.push(tokens.length); 从上面代码可知,我们知道 tokens = [["#", "msg", 0, 8]];
因此 spaces = [1]; tokens.push([ 'text', chr, start, start + 1 ]); 执行后 tokens的值变为如下:
tokens = [["#", "msg", 0, 8], ['text', ' ', 8, 9]]; start +=1; 因此 start = 9;
如果 chr === '\n'; 则执行 stripSpace()方法,这里为false,因此不执行。
继续执行如下代码:

if (!scanner.scan(openingTagRe))
      break;
openingTagRe的值为:openingTagRe = /\{\{\s*/;

scan 函数代码如下:

Scanner.prototype.scan = function scan (re) {
      var match = this.tail.match(re);

      if (!match || match.index !== 0)
        return '';

      var string = match[0];

      this.tail = this.tail.substring(string.length);
      this.pos += string.length;

      return string;
};

因此 re = /\{\{\s*/; 从上面可知,我们的scanner的值为如下:

scanner = {
      pos: 9,
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      tail: "{{.}} * <div>{{name}}</div> {{/msg}}"
};

继续执行 Scanner.prototype.scan() 函数内部代码:
var match = this.tail.match(re) = "{{.}} * <div>{{name}}</div> {{/msg}}".match(/\{\{\s*/);
因此 match的匹配结果如下:

var match = [
      "{{",
      index: 0,
      groups: undefined,
      input: "{{.}} * <div>{{name}}</div> {{/msg}}"
];
var string = match[0] = "{{";
this.tail = this.tail.substring(string.length);

因此 this.tail = "{{.}} * <div>{{name}}</div> {{/msg}}".substring(2);
最后 this.tail = ".}} * <div>{{name}}</div> {{/msg}}";
this.pos += string.length; 因此 this.pos = 9 + 2 = 11;
最后返回 return string; 即返回 "{{";
因此 此时 scanner 的值变为如下:

scanner = {
      pos: 11,
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      tail: ".}} * <div>{{name}}</div> {{/msg}}"
};

接着继续执行代码:type = scanner.scan(tagRe) || 'name';
tagRe 在页面是定义的正则为:/#|\^|\/|>|\{|&|=|!/;
因此又会执行 Scanner.prototype.scan = function scan (re) {}, 代码如下:

Scanner.prototype.scan = function scan (re) {
      var match = this.tail.match(re);
      if (!match || match.index !== 0)
        return '';
      var string = match[0];
      this.tail = this.tail.substring(string.length);
      this.pos += string.length;
      return string;
}

由上面可知: 

scanner = {
      pos: 11,
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      tail: ".}} * <div>{{name}}</div> {{/msg}}"
};
re = /#|\^|\/|>|\{|&|=|!/;
因此 var match = this.tail.match(re) = ".}} * <div>{{name}}</div> {{/msg}}".match(/#|\^|\/|>|\{|&|=|!/);
var match = [
      ">",
      index: 10,
      groups: undefined,
      input: ".}} * <div>{{name}}</div> {{/msg}}"
];

如上代码:match.index === 10; 因此 不等于0;所以就直接返回 ''; 跳出函数,因此 type = 'name' 了;
继续执行如下代码:scanner.scan(whiteRe); whiteRe = /\s*/;
还是一样执行 Scanner.prototype.scan = function scan (re) {} 函数;
因此 var match = ".}} * <div>{{name}}</div> {{/msg}}".match(/\s*/);

var match = [
      '',
      groups: undefined,
      index: 0,
      input: ".}} * <div>{{name}}</div> {{/msg}}"
];

再接着执行代码 var string = match[0] = '';
this.tail = this.tail.substring(0) = ".}} * <div>{{name}}</div> {{/msg}}";
this.pos += string.length = 11 + 0 = 11;
此时 scanner 的值,和上一步的值一样:

scanner = {
      pos: 11,
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      tail: ".}} * <div>{{name}}</div> {{/msg}}"
 };

最后返回 空字符串 '';
如上我们知道 type = 'name'; 因此 继续进入如下else代码:

if (type === '=') {

} else if (type === '{') {

} else {
      value = scanner.scanUntil(closingTagRe);
}

再来看下 scanUntil 代码如下:

Scanner.prototype.scanUntil = function scanUntil (re) {
      var index = this.tail.search(re), match;
      switch (index) {
        case -1:
          match = this.tail;
          this.tail = '';
          break;
        case 0:
          match = '';
          break;
        default:
          match = this.tail.substring(0, index);
          this.tail = this.tail.substring(index);
      }
      this.pos += match.length;
      return match;
};

如上代码:closingTagRe = /\s*\}\}/;
var index = this.tail.search(re) = ".}} * <div>{{name}}</div> {{/msg}}".search(/\s*\}\}/) = 1;
因此进入 default语句内部。
因此 match = this.tail.substring(0, index) = ".}} * <div>{{name}}</div> {{/msg}}".substring(0, 1);
match = '.';
this.tail = this.tail.substring(index) = ".}} * <div>{{name}}</div> {{/msg}}".substring(1);
因此 this.tail = "}} * <div>{{name}}</div> {{/msg}}";
this.pos += match.length = 11 + 1 = 12; 最后 return match; 返回 '.';
此时 scanner的值为如下:

scanner = {
      pos: 12,
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      tail: "}} * <div>{{name}}</div> {{/msg}}"
};

接着继续执行 if (!scanner.scan(closingTagRe)){} 代码; closingTagRe = /\s*\}\}/; 

Scanner.prototype.scan = function scan (re) {
      var match = this.tail.match(re);
      if (!match || match.index !== 0)
        return '';
      var string = match[0];
      this.tail = this.tail.substring(string.length);
      this.pos += string.length;
      return string;
 };

因此调用 Scanner.prototype.scan() 函数后,

var match = "}} * <div>{{name}}</div> {{/msg}}".match(/\s*\}\}/);
    var match = [
      "}}",
      groups: undefined,
      index: 0,
      input: "}} * <div>{{name}}</div> {{/msg}}"
    ];
 var string = match[0] = "}}";
 this.tail = this.tail.substring(string.length);

因此 this.tail = "}} * <div>{{name}}</div> {{/msg}}".substring(2);
最后 this.tail = " * <div>{{name}}</div> {{/msg}}";
this.pos = 12 + 2 = 14;
最后 return string; 返回 "}}";
此时 scanner的值为如下:

scanner = {
      pos: 14,
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      tail: " * <div>{{name}}</div> {{/msg}}"
 };

继续执行代码:token = [ type, value, start, scanner.pos ];
因此 token = ['name', '.', 9, 14];
继续往下执行代码:
tokens.push(token);

因此此时 tokens = [
      ["#", "msg", 0, 8], 
      ['text', ' ', 8, 9],
      ["name", ".", 9, 14]
 ];

此时 type = 'name'; 因此 nonSpace = true; 执行完成后。继续while循环。

第三次while循环

此时scanner值为如下:

scanner = {
    pos: 14,
    string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
    tail: " * <div>{{name}}</div> {{/msg}}"
  };

start = scanner.pos; 因此 start = 14;
value = scanner.scanUntil(openingTagRe); 执行这句代码:
openingTagRe = /\{\{\s*/;

Scanner.prototype.scanUntil = function scanUntil (re) {
    var index = this.tail.search(re), match;
    switch (index) {
      case -1:
        match = this.tail;
        this.tail = '';
        break;
      case 0:
        match = '';
        break;
      default:
        match = this.tail.substring(0, index);
        this.tail = this.tail.substring(index);
    }
    this.pos += match.length;
    return match;
  };

var index = this.tail.search(re) = " * <div>{{name}}</div> {{/msg}}".search(/\{\{\s*/);
因此 var index = 8;
然后又继续进入 default语句;此时 match = this.tail.substring(0, index);
match = " * <div>{{name}}</div> {{/msg}}".substring(0, 8) = " * <div>";
this.tail = this.tail.substring(index) = " * <div>{{name}}</div> {{/msg}}".substring(8);
因此 this.tail = "{{name}}</div> {{/msg}}";
this.pos += match.length = 14 + 8 = 22;
因此 此时scanner值为如下:

scanner = {
    pos: 22,
    string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
    tail: "{{name}}</div> {{/msg}}"
  };

最后返回 " * <div>" 赋值给 value;
因此继续进入 if (value) {} 代码内部:

if (value) {
    for (var i = 0, valueLength = value.length; i < valueLength; ++i) {
      chr = value.charAt(i);
      if (isWhitespace(chr)) {
        spaces.push(tokens.length);
      } else {
        nonSpace = true;
      }
      tokens.push([ 'text', chr, start, start + 1 ]);
      start += 1;
      // Check for whitespace on the current line.
      if (chr === '\n')
        stripSpace();
    }
  }
  var regExpTest = RegExp.prototype.test;
  function testRegExp (re, string) {
    return regExpTest.call(re, string);
  }

  var nonSpaceRe = /\S/;
  function isWhitespace (string) {
    return !testRegExp(nonSpaceRe, string);
  }
而此时 value.length = 8了;因此在for语句需要循环8次。

    i = 0:chr = value.charAt(i) = " * <div>".charAt(0) = " "; 执行 isWhitespace(chr); 函数代码,如下代码:
    RegExp.prototype.test.call(/\S/, ' '); 判断 ' ' 是否是非空白字符,因此返回false,因此 !false 就是true了。
    因此 执行 spaces.push(tokens.length); 
    之前tokens = [["#", "msg", 0, 8],["text", " ", 8, 9],["name", ".", 9, 14]]; spaces = [1];
    因此此时 spaces = [1, 3]; 了。
    接着执行 tokens.push([ 'text', chr, start, start + 1 ]);
    因此 tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
    ];
    start += 1; 因此 start = 15;

    i = 1:chr = value.charAt(i) = " * <div>".charAt(1) = "*"; 执行 isWhitespace(chr); 返回false; 因此进入else
    语句; 此时:nonSpace = true; 继续执行代码:tokens.push([ 'text', chr, start, start + 1 ]); 因此tokens的值变为
    如下:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16]
    ];
    start += 1; 因此 start = 16;

    i = 2:chr = value.charAt(i) = " * <div>".charAt(2) = " "; 执行 isWhitespace(chr); 返回true; 和第一步一样,
    因此 执行 spaces.push(tokens.length); 因此 spaces.push(tokens.length); 即 spaces = [1, 3, 5];
    继续执行代码:tokens.push([ 'text', chr, start, start + 1 ]); 因此tokens的值变为如下:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17]
    ];
    start +=1; 因此 start = 17;

    i = 3: chr = value.charAt(i) = " * <div>".charAt(3) = "<"; 执行 isWhitespace(chr); 返回false, 因此进入else
    语句。此时:nonSpace = true; 继续执行代码:tokens.push([ 'text', chr, start, start + 1 ]); 因此tokens的值变为
    如下:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18]
    ];
    start +=1; 因此 start = 18;

    i = 4: 同理,和第三步一样。因此 chr = 'd'; 因此tokens的值变为
    如下:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19]
    ];
    start +=1; 因此 start = 19;

    i = 5; 同理,和第三步一样。因此 chr = 'i'; 最后tokens的值变为:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20]
    ];
    start +=1; 因此 start = 20;

    i = 6; 同理,和第三步一样。因此 chr = 'v'; 最后tokens的值变为:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
    ];
    start +=1; 因此 start = 21;

    i = 7; 同理,和第三步一样。因此 chr = '>'; 最后tokens的值变为:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22]
    ];
    start +=1; 因此 start = 22;
ng: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      tail: "{{name}}</div> {{/msg}}"
    }

继续执行代码:if (!scanner.scan(openingTagRe)) {}; 因此进入 Scanner.prototype.scan = function scan (re) {} 函数代码内部。源码如下:

Scanner.prototype.scan = function scan (re) {
      var match = this.tail.match(re);
      if (!match || match.index !== 0)
        return '';
      var string = match[0];
      this.tail = this.tail.substring(string.length);
      this.pos += string.length;
      return string;
    };

re 值 = /\{\{\s*/; 此时 scanner 值为如下:

scanner = {
      pos: 22,
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      tail: "{{name}}</div> {{/msg}}"
    }

因此 var match = "{{name}}</div> {{/msg}}".match(/\{\{\s*/);

var match = [
      "{{",
      index: 0,
      groups: undefined,
      input: "{{name}}</div> {{/msg}}"
    ];

var string = match[0]; 因此 var string = "{{";
this.tail = this.tail.substring(string.length) = "{{name}}</div> {{/msg}}".substring(2);
因此:this.tail = "name}}</div> {{/msg}}";
this.pos += string.length; this.pos = 22 + 2 = 24; 最后返回 "{{". 因此此时 scanner的值变为如下:

scanner = {
      pos: 24,
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      tail: "name}}</div> {{/msg}}"
    };

继续执行代码:type = scanner.scan(tagRe) || 'name';
函数代码如下:

Scanner.prototype.scan = function scan (re) {
      var match = this.tail.match(re);
      if (!match || match.index !== 0)
        return '';
      var string = match[0];
      this.tail = this.tail.substring(string.length);
      this.pos += string.length;
      return string;
    };

如上:tagRe = /#|\^|\/|>|\{|&|=|!/; this.tail = "name}}</div> {{/msg}}";
因此 var match = "name}}</div> {{/msg}}".match(/#|\^|\/|>|\{|&|=|!/);

var match = [
      '/',
      index: 7,
      groups: undefined,
      input: "name}}</div> {{/msg}}"
    ];

由于 match.index !== 0; 因此直接 返回 ''; 此时 type = 'name';
继续执行代码:scanner.scan(whiteRe); whiteRe 的值 = /\s*/; 然后又调用 Scanner.prototype.scan 函数。
因此 var match = "name}}</div> {{/msg}}".match(/\s*/);

var match = [
      "",
      index: 0,
      groups: undefined,
      input: "name}}</div> {{/msg}}"
    ];
    var string = match[0] = "";
    this.tail = this.tail.substring(string.length);
    this.tail = this.tail.substring(0);
    this.tail = "name}}</div> {{/msg}}";
    this.pos = 24;

最后 返回 return string; 返回 "";
此时 scanner 的值变为如下:

scanner = {
      pos: 24,
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
      tail: "name}}</div> {{/msg}}"
    };

由于上面 type = "name"; 因此 就会执行 else 语句代码,因此 执行 value = scanner.scanUntil(closingTagRe);

Scanner.prototype.scanUntil = function scanUntil (re) {
      var index = this.tail.search(re), match;
      switch (index) {
        case -1:
          match = this.tail;
          this.tail = '';
          break;
        case 0:
          match = '';
          break;
        default:
          match = this.tail.substring(0, index);
          this.tail = this.tail.substring(index);
      }
      this.pos += match.length;
      return match;
    };
    var closingTagRe = /\s*\}\}/;

因此继续调用 Scanner.prototype.scanUntil 函数。
因此 var index = "name}}</div> {{/msg}}".search(/\s*\}\}/) = 4;
因此 继续进入 default语句代码;
match = "name}}</div> {{/msg}}".substring(0, 4);
match = "name";
this.tail = "name}}</div> {{/msg}}".substring(4) = "}}</div> {{/msg}}";
this.pos += match.length = 24 + 4 = 28;
最后我们返回 return "name"; 此时 scanner 的值变为如下:

scanner = {
      pos: 28,
      tail: "}}</div> {{/msg}}",
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
    };

因此 value = "name";
继续执行下面的代码:
if (!scanner.scan(closingTagRe)) {};
又会调用 Scanner.prototype.scan = function scan (re) {} 函数代码了。
代码如下:

Scanner.prototype.scan = function scan (re) {
      var match = this.tail.match(re);
      if (!match || match.index !== 0)
        return '';
      var string = match[0];
      this.tail = this.tail.substring(string.length);
      this.pos += string.length;
      return string;
    };

因此值分别为如下:

var match = "}}</div> {{/msg}}".match(/\s*\}\}/);
    var match = [
      "}}",
      index: 0,
      groups: undefined,
      input: "}}</div> {{/msg}}"
    ];
    var string = match[0] = "}}";
    this.tail = this.tail.substring(string.length) = "}}</div> {{/msg}}".substring(2);
    this.tail = "</div> {{/msg}}";
    this.pos += string.length; this.pos = 28 + 2 = 30;

最后我们返回 "}}". 因此此时 scanner 的值变为如下:

scanner = {
      pos: 30,
      tail: "</div> {{/msg}}",
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
    };

继续执行代码: token = [ type, value, start, scanner.pos ]; 代码;因此token的值为如下:
token = ['name', 'name', 22, 30];
继续执行 tokens.push(token); 因此 tokens的值变为如下:

tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22],
      ["name", "name", 22, 30]
    ];

由于 type = "name"; 因此 nonSpace = true;

第四次while循环

此时 scanner = {
    pos: 30,
    string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}",
    tail: "</div> {{/msg}}"
  };
  start = scanner.pos; start = 30;
  // Match any text between tags.
  value = scanner.scanUntil(openingTagRe);
  openingTagRe 值为:openingTagRe = /\{\{\s*/;

调用 scanUntil 函数代码如下:

Scanner.prototype.scanUntil = function scanUntil (re) {
    var index = this.tail.search(re), match;
    switch (index) {
      case -1:
        match = this.tail;
        this.tail = '';
        break;
      case 0:
        match = '';
        break;
      default:
        match = this.tail.substring(0, index);
        this.tail = this.tail.substring(index);
    }
    this.pos += match.length;
    return match;
  };
  var index = "</div> {{/msg}}".search(/\{\{\s*/);
  var index = 7;

因此 进入 default 语句代码:
match = this.tail.substring(0, index) = "</div> {{/msg}}".substring(0, 7);
因此 match = "</div> ";
this.tail = this.tail.substring(index) = "</div> {{/msg}}".substring(7);
this.tail = "{{/msg}}";
this.pos += match.length = 30 + 7 = 37;
最后返回 return match; 因此 返回 "</div> ";
此时 scanner 的值变为如下:

scanner = {
    pos: 37,
    tail: "{{/msg}}",
    string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
  };

因此 value = "</div> ";
因此会进入 if (value) {}; 语句代码,如下所示:

if (value) {
    for (var i = 0, valueLength = value.length; i < valueLength; ++i) {
      chr = value.charAt(i);
      if (isWhitespace(chr)) {
        spaces.push(tokens.length);
      } else {
        nonSpace = true;
      }
      tokens.push([ 'text', chr, start, start + 1 ]);
      start += 1;
      // Check for whitespace on the current line.
      if (chr === '\n')
        stripSpace();
    }
  }

由于value的值为 "</div> "; 长度为7. 因此会在内部for循环中循环7次。依次看下:

1. i = 0; 
    执行 chr = value.charAt(i); 因此 chr = "<"; 此时 chr 不是空白字符,因此该 isWhitespace(chr) 函数返回false。
    因此 nonSpace = true; 接着执行:tokens.push([ 'text', chr, start, start + 1 ]); 因此 tokens的值变为如下:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22],
      ["name", "name", 22, 30],
      ["text", "<", 30, 31]
    ];
    start += 1; 因此 start 值为 31.

    2. i = 1;
    同第一步一样,因此 chr = "/"; 因此 tokens的值变为如下:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22],
      ["name", "name", 22, 30],
      ["text", "<", 30, 31],
      ["text", "/", 31, 32]
    ];
    start += 1; 因此 start 值为 32.

    3. i = 2;
    同第一步一样,因此 chr = "d"; 因此 tokens的值变为如下:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22],
      ["name", "name", 22, 30],
      ["text", "<", 30, 31],
      ["text", "/", 31, 32],
      ["text", "d", 32, 33]
    ];
    start += 1; 因此 start 值为 33.

    4. i = 3;
    同第一步一样,因此 chr = "i"; 因此 tokens的值变为如下:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22],
      ["name", "name", 22, 30],
      ["text", "<", 30, 31],
      ["text", "/", 31, 32],
      ["text", "d", 32, 33],
      ["text", "i", 33, 34]
    ];
    start += 1; 因此 start 值为 34.

    5. i = 4;
    同第一步一样,因此 chr = "i"; 因此 tokens的值变为如下:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22],
      ["name", "name", 22, 30],
      ["text", "<", 30, 31],
      ["text", "/", 31, 32],
      ["text", "d", 32, 33],
      ["text", "i", 33, 34],
      ["text", "v", 34, 35]
    ];
    start += 1; 因此 start 值为 35.

    6. i = 5;
    同第一步一样,因此 chr = ">"; 因此 tokens的值变为如下:
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22],
      ["name", "name", 22, 30],
      ["text", "<", 30, 31],
      ["text", "/", 31, 32],
      ["text", "d", 32, 33],
      ["text", "i", 33, 34],
      ["text", "v", 34, 35],
      ["text", ">", 35, 36]
    ];
    start += 1; 因此 start 值为 36.

    7. i = 6
    执行 chr = value.charAt(i); 因此 chr = " "; 此时 chr 为空白字符,因此会执行 isWhitespace(chr) 函数返回true。
    因此执行 spaces.push(tokens.length); 因此 spaces 的值为:
    spaces = [1, 3, 5, 18]; 
    继续执行代码:tokens.push([ 'text', chr, start, start + 1 ]);
    因此
    tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22],
      ["name", "name", 22, 30],
      ["text", "<", 30, 31],
      ["text", "/", 31, 32],
      ["text", "d", 32, 33],
      ["text", "i", 33, 34],
      ["text", "v", 34, 35],
      ["text", ">", 35, 36],
      ["text", " ", 36, 37]
    ];
    start += 1; 因此 start 值为37。

接着执行代码: if (!scanner.scan(openingTagRe)) { break; }
openingTagRe 值为:openingTagRe = /\{\{\s*/;
Scanner.prototype.scan() 函数代码如下:

Scanner.prototype.scan = function scan (re) {
      var match = this.tail.match(re);

      if (!match || match.index !== 0)
        return '';

      var string = match[0];

      this.tail = this.tail.substring(string.length);
      this.pos += string.length;

      return string;
    };

由上可知,此时 scanner 的值为 = {
   pos: 37,
   tail: "{{/msg}}",
   string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
};
因此 var match = "{{/msg}}".match(/\{\{\s*/);

var match = [
      "{{",
      index: 0,
      groups: undefined,
      input: "{{/msg}}"
    ];
    var string = match[0] = "{{";
    this.tail = this.tail.substring(string.length);
    this.tail = "{{/msg}}".substring(2) = "/msg}}";
    this.pos += 2 = 39;

最后返回 return string; 就返回了 "{{"; 此时 scannel的值变为如下:

scanner = {
      pos: 39,
      tail: "/msg}}",
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
    };

再执行代码:type = scanner.scan(tagRe) || 'name';
tagRe 的值 = /#|\^|\/|>|\{|&|=|!/; 因此会继续调用 Scanner.prototype.scan = function scan (re) {} 函数。
继续执行该函数内部的代码,因此:

var match = this.tail.match(re); var match = "/msg}}".match(/#|\^|\/|>|\{|&|=|!/);
    var match = [
      "/",
      index: 0,
      groups: undefined,
      input: "/msg}}"
    ];
    var string = match[0] = "/";
    this.tail = this.tail.substring(string.length) = "/msg}}".substring(1);
    this.tail = "msg}}";
    this.pos += 1; 因此 this.pos = 40;

最后返回 "/"; 因此 type = '/';
此时 scanner 的值为如下:

scanner = {
      pos: 40,
      tail: "msg}}",
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
    };

再执行代码:scanner.scan(whiteRe); whiteRe 的值 = /\s*/;
因此又进入 scan函数内部依次执行如下:

var match = this.tail.match(re) = "msg}}".match(/\s*/);
    var match = [
      "",
      index: 0,
      groups: undefined,
      input: "msg}}"
    ];
    var string = match[0]; var string = "";
    this.tail = this.tail.substring(string.length);
    this.tail = "/msg}}".substring(0) = "/msg}}";
    this.pos += string.length; this.pos = 40;

最后返回 return string; 返回 ""; 跳出该函数,继续执行下一步代码。

此时 scanner = {
      pos: 40,
      tail: "msg}}",
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
    };

因此代码执行到 if (type === '=') {} else if(type === '{') {} else {} 这里了
由于 type = '/'; 因此代码执行到 else 内部了。
执行代码:value = scanner.scanUntil(closingTagRe);
closingTagRe 值为 = /\s*\}\}/;
Scanner.prototype.scanUntil 函数如下:

Scanner.prototype.scanUntil = function scanUntil (re) {
      var index = this.tail.search(re), match;
      switch (index) {
        case -1:
          match = this.tail;
          this.tail = '';
          break;
        case 0:
          match = '';
          break;
        default:
          match = this.tail.substring(0, index);
          this.tail = this.tail.substring(index);
      }
      this.pos += match.length;
      return match;
    };

因此 var index = "msg}}".search(/\s*\}\}/) = 3;
执行到 default语句代码内。
因此 match = this.tail.substring(0, index) = "msg}}".substring(0, 3) = "msg";
this.tail = "msg}}".substring(3) = "}}";
this.pos += match.length; this.pos = 40 + 3 = 43;
最后返回 return match; 因此 返回 "msg"; 此次此刻 scanner的值变为如下:

scanner = {
      pos: 43,
      tail: "}}",
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
    };

现在跳出 Scanner.prototype.scanUntil 函数代码,执行下一步代码:如下:
if (!scanner.scan(closingTagRe)) {}; 因此会调用 scan 函数代码。
closingTagRe 值为 = /\s*\}\}/;

Scanner.prototype.scan = function scan (re) {
      var match = this.tail.match(re);
      if (!match || match.index !== 0)
        return '';
      var string = match[0];
      this.tail = this.tail.substring(string.length);
      this.pos += string.length;
      return string;
    };

因此 var match = "}}".match(/\s*\}\}/);

var match = [
      "}}",
      index: 0,
      groups: undefined,
      input: "}}"
    ];
    var string = match[0] = "}}";
    this.tail = this.tail.substring(string.length) = "}}".substring(2) = "";
    this.pos = 43 + 2 = 45;

最后返回 return string; 因此返回 "}}". 此时scanner的值变为如下:

scanner = {
      pos: 45,
      string: "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}"
      tail: ""
    };

跳出 Scanner.prototype.scan 函数代码后,接着执行下面的代码:
token = [ type, value, start, scanner.pos ];
tokens.push(token);
因此 token = ['/', 'msg', 37, 45];

tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22],
      ["name", "name", 22, 30],
      ["text", "<", 30, 31],
      ["text", "/", 31, 32],
      ["text", "d", 32, 33],
      ["text", "i", 33, 34],
      ["text", "v", 34, 35],
      ["text", ">", 35, 36],
      ["text", " ", 36, 37],
      ['/', 'msg', 37, 45]
    ];

此时此刻 type = '/'; 因此 会执行 

else if (type === '/') {
      // Check section nesting.
      openSection = sections.pop();
      if (!openSection)
        throw new Error('Unopened section "' + value + '" at ' + start);
      if (openSection[1] !== value)
        throw new Error('Unclosed section "' + openSection[1] + '" at ' + start);

else if 内部的代码,如上所示:执行一些清空操作。

因此 这个时候会跳出while循环了,因为所有的字符都解析完毕了。最后一句代码:return nestTokens(squashTokens(tokens));

我们会调用 nestTokens()函数,在调用该函数之前会调用 squashTokens(tokens);
squashTokens 函数代码如下:

function squashTokens (tokens) {
      var squashedTokens = [];
      var token, lastToken;
      for (var i = 0, numTokens = tokens.length; i < numTokens; ++i) {
        token = tokens[i];
        if (token) {
          if (token[0] === 'text' && lastToken && lastToken[0] === 'text') {
            lastToken[1] += token[1];
            lastToken[3] = token[3];
          } else {
            squashedTokens.push(token);
            lastToken = token;
          }
        }
      }
      return squashedTokens;
    }

由上面的一系列操作,我们知道tokens的值为如下:

tokens = [
      ["#", "msg", 0, 8],
      ["text", " ", 8, 9],
      ["name", ".", 9, 14],
      ["text", " ", 14, 15],
      ["text", "*", 15, 16],
      ["text", " ", 16, 17],
      ["text", "<", 17, 18],
      ["text", "d", 18, 19],
      ["text", "i", 19, 20],
      ["text", "v", 20, 21],
      ["text", ">", 21, 22],
      ["name", "name", 22, 30],
      ["text", "<", 30, 31],
      ["text", "/", 31, 32],
      ["text", "d", 32, 33],
      ["text", "i", 33, 34],
      ["text", "v", 34, 35],
      ["text", ">", 35, 36],
      ["text", " ", 36, 37],
      ['/', 'msg', 37, 45]
    ];

首先在函数内部定义一个新数组 var squashedTokens = []; 然后循环传进来的tokens的值。tokens的长度为20.
为了更清楚的理解具体做了哪些事情,我们继续一步步把for循环拆开理解。如下所示:

i = 0; 
      token = tokens[0] = ["#", "msg", 0, 8];
      因此进入 if (token) 内部代码,由于是第一次循环,所以 lastToken 为undefined,因此进入else语句代码;
      squashedTokens.push(token); 因此 squashedTokens = [ ["#", "msg", 0, 8] ];
      lastToken = token; 因此 lastToken = ["#", "msg", 0, 8];

      i = 1;
      token = tokens[1] = ["text", " ", 8, 9];
      进入if语句,if (token) 内部代码,这个时候 lastToken 有值了,token[0] === 'text' 为true,lastToken也为true,
      但是 lastToken = ["#", "msg", 0, 8]; 因此 lastToken[0] === 'text' 为false。因此还是进入else语句代码:
      因此 squashedTokens = [ ["#", "msg", 0, 8], ["text", " ", 8, 9] ]; lastToken = ["text", " ", 8, 9];

      i = 2;
      token = tokens[2] = ["name", ".", 9, 14];
      进入if语句代码,由于 token[0] === "name"; 因此进入else语句,此时 squashedTokens.push(token); 值为如下:
      ```
      squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14]
      ];
      lastToken = ["name", ".", 9, 14];
      ```
      i = 3;
      token = tokens[3] = ["text", " ", 14, 15];
      进入if(token)语句代码,token[0] === 'text' 为true; lastToken 也有值,为true,lastToken[0] === 'name' 为false,因此进入else语句代码, 因此 squashedTokens 和 lastToken 值分别为如下:
      ```
      squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " ", 14, 15]
      ];
      lastToken = ["text", " ", 14, 15];
      ```
      i = 4;
      token = tokens[4] = ["text", "*", 15, 16];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true,因此进入 第二个if
      语句代码:执行 lastToken[1] += token[1]; lastToken[3] = token[3]; 代码;
      即:lastToken[1] = " " + "*" = " *"; lastToken[3] = 16; 因此 lastToken = ["text", " *", 14, 16];
      ```
      因此 squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " *", 14, 16]
      ];
      ```
      这里明明没有进else内部代码,为什么这边 squashedTokens 对象值也发生变化呢?那是因为 代码里面对象数组的复制只是
      浅拷贝,如else内部代码:lastToken = token; 最后一次的token 和 lastToken 指向了同一个指针引用。因此也会导致数组
      squashedTokens 的某项的也会发生改变。

      i = 5;
      token = tokens[5] = ["text", " ", 16, 17];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true,
      因此 lastToken[1] += token[1]; lastToken[1] = " *" + " " = " * ";
      lastToken[3] = 17; 即:lastToken = ["text", " * ", 14, 17];
      ```
      因此 squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * ", 14, 17]
      ];
      ```
      i = 6;
      token = tokens[6] = ["text", "<", 17, 18];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true,
      因此 lastToken[1] += token[1]; lastToken[1] = " * " + "<" = " * <";
      lastToken[3] = 18; 即:lastToken = ["text", " * <", 14, 18];
      ```
      因此 squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <", 14, 18]
      ];
      ```
      i = 7;
      token = tokens[7] = ["text", "d", 18, 19];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true,
      因此 lastToken[1] += token[1]; lastToken[1] = " * <" + "d" = " * <d";
      lastToken[3] = 19; 即:lastToken = ["text", " * <d", 14, 19];
      ```
      因此 squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <d", 14, 19]
      ];
      ```

      i = 8;
      token = tokens[8] = ["text", "i", 19, 20];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true;
      因此 lastToken[1] += token[1]; lastToken[1] = " * <d" + "i" = " * <di";
      lastToken[3] = 20; 即:lastToken = ["text", " * <di", 14, 20];
      ```
      因此 squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <di", 14, 20]
      ];
      ```
      i = 9;
      token = tokens[9] = ["text", "v", 20, 21];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true;
      因此 lastToken[1] += token[1]; lastToken[1] = " * <di" + "v" = " * <div";
      lastToken[3] = 21; 即:lastToken = ["text", " * <div", 14, 21];
      ```
      因此 squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div", 14, 21]
      ]
      ```

      i = 10;
      token = tokens[10] = ["text", ">", 21, 22];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true;
      因此 lastToken[1] += token[1]; lastToken[1] = " * <div" + ">" = " * <div>";
      lastToken[3] = 22; 即:lastToken = ["text", " * <div>", 14, 22];
      ```
      因此 squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22]
      ]
      ```
      i = 11;
      token = tokens[11] = ["name", "name", 22, 30];
      token[0] === 'text' 为false, 因此进入else语句代码:squashedTokens.push(token); lastToken = token;
      ```
      因此 squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22],
        ["name", "name", 22, 30]
      ];
      lastToken = ["name", "name", 22, 30];
      ```
      i = 12;
      token = tokens[12] = ["text", "<", 30, 31];
      由于上一步 lastToken[0] = "name"; 因此进入else语句代码,即:
      ```
      squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22],
        ["name", "name", 22, 30],
        ["text", "<", 30, 31]
      ];
      lastToken = ["text", "<", 30, 31];
      ```
      i = 13;
      token = tokens[13] = ["text", "/", 31, 32];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true;
      因此:lastToken[1] += token[1]; 即:lastToken[1] = "<" + "/" = "</";
      lastToken[3] = token[3]; 即:lastToken[3] = 32; 因此 lastToken = ["text", "</", 30, 32];
      ```
      squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22],
        ["name", "name", 22, 30],
        ["text", "</", 30, 32]
      ];
      ```
      i = 14;
      token = tokens[14] = ["text", "d", 32, 33];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true;
      因此 lastToken[1] += token[1]; 即:lastToken[1] = "</" + "d" = "</d";
      lastToken[3] = token[3]; 即:lastToken[3] = 33; 因此 lastToken = ["text", "</d", 30, 33];
      ```
      squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22],
        ["name", "name", 22, 30],
        ["text", "</d", 30, 33]
      ];
      ```
      i = 15;
      token = tokens[15] = ["text", "i", 33, 34];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true;
      因此 lastToken[1] += token[1]; 即:lastToken[1] = "</d" + "i" = "</di";
      lastToken[3] = token[3]; 即:lastToken[3] = 34; 因此 lastToken = ["text", "</di", 30, 34];
      ```
      squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22],
        ["name", "name", 22, 30],
        ["text", "</di", 30, 34]
      ];
      ```
      i = 16;
      token = tokens[16] = ["text", "v", 34, 35];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true;
      因此 lastToken[1] += token[1]; 即:lastToken[1] = "</di" + "v" = "</div";
      lastToken[3] = token[3]; 即:lastToken[3] = 35; 因此 lastToken = ["text", "</div", 30, 35];
      ```
      squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22],
        ["name", "name", 22, 30],
        ["text", "</div", 30, 35]
      ];
      ```
      i = 17;
      token = tokens[17] = ["text", ">", 35, 36];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true;
      因此 lastToken[1] += token[1]; 即:lastToken[1] = "</div" + ">" = "</div>";
      lastToken[3] = token[3]; 即:lastToken[3] = 36; 因此 lastToken = ["text", "</div>", 30, 36];
      ```
      squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22],
        ["name", "name", 22, 30],
        ["text", "</div>", 30, 36]
      ];
      ```
      i = 18;
      token = tokens[18] = ["text", " ", 36, 37];
      token[0] === 'text' 为true; lastToken 也有值,为true, lastToken[0] === 'text' 也为true;
      因此 lastToken[1] += token[1]; 即:lastToken[1] = "</div>" + " " = "</div> ";
      lastToken[3] = token[3]; 即:lastToken[3] = 37; 因此 lastToken = ["text", "</div> ", 30, 37];
      ```
      squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22],
        ["name", "name", 22, 30],
        ["text", "</div> ", 30, 37]
      ];
      ```
      i = 19;
      token = tokens[19] = ['/', 'msg', 37, 45];
      token[0] === 'text' 为false,因此进入else语句代码。即:squashedTokens.push(token); lastToken = token;
      ```
      因此:squashedTokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22],
        ["name", "name", 22, 30],
        ["text", "</div> ", 30, 37]
        ['/', 'msg', 37, 45]
      ];
      lastToken = ['/', 'msg', 37, 45];

最后我们的代码返回 return squashedTokens;

最后一步我们就是要调用 nestTokens 函数了,函数代码如下:

function nestTokens (tokens) {
        var nestedTokens = [];
        var collector = nestedTokens;
        var sections = [];
        var token, section;
        for (var i = 0, numTokens = tokens.length; i < numTokens; ++i) {
          token = tokens[i];
          switch (token[0]) {
            case '#':
            case '^':
              collector.push(token);
              sections.push(token);
              collector = token[4] = [];
              break;
            case '/':
              section = sections.pop();
              section[5] = token[2];
              collector = sections.length > 0 ? sections[sections.length - 1][4] : nestedTokens;
              break;
            default:
              collector.push(token);
          }
        }
        return nestedTokens;
      }

tokens 值就是我们上面返回 return squashedTokens;值了,因此:

tokens = [
        ["#", "msg", 0, 8],
        ["text", " ", 8, 9],
        ["name", ".", 9, 14],
        ["text", " * <div>", 14, 22],
        ["name", "name", 22, 30],
        ["text", "</div> ", 30, 37],
        ['/', 'msg', 37, 45]
      ];

然后for循环遍历,因为数组的长度为7,因此循环遍历7次。再分别看下:

i = 0;
token = ["#", "msg", 0, 8];
collector.push(token); 因此:collector = [ ["#", "msg", 0, 8] ];
sections.push(token); 因此:sections =  [ ["#", "msg", 0, 8] ];
执行:collector = token[4] = []; 
因此 collector = []; sections = [ ["#", "msg", 0, 8, [] ] ];
但是此时 nestedTokens = [ ["#", "msg", 0, 8, [] ] ];

为什么是这样的呢?按道理来说 var nestedTokens = []; var collector = nestedTokens; 这两个数组是浅拷贝,但是为什么
collector数组被置空了,为什么 nestedTokens 数组还是有数据呢?我们在理解之前,我们可以看如下demo来理解下:
```
var arr1 = [];
var arr2 = arr1;
var token = [1];
arr2.push(token);
console.log(arr2); // [ [1] ]
console.log(arr1); // [ [1] ]

arr2 = token[1] = [];
console.log(token); // [ [1], []]
console.log(arr2); // []
console.log(arr1); // [ [1], []]
console.log(arr2.__proto__ === arr1.__proto__); // ture
```
如上我们可以看到,上面两个demo是仿照我们代码的意思来的,其结果是一样的,虽然其中一个数组值为空了,但是另外一个数组并没有。
那是因为 arr2 = token[1] = []; 这句代码,我们上面的token的值为 token = [1]; 这样的,然后设置 token[1] = []; 因此
token = [1, []]; 最后把token[1] 的值赋值给 arr2了,因此arr2的值变为 []; 但是 arr1.__proto__ === arr2.__proto__
是相等的,也就是他们俩还是指向了同一个引用,因为数组或对象 比较的不是值,而是是否是同一个引用。引用的还是同一个token对象。
所以 arr2 = [], 但是 arr1 = [ [1], [] ]; 

i = 1;
token = ["text", " ", 8, 9];
token[0] = "text", 因此进入default语句代码,因此 collector = [["text", " ", 8, 9]];
由于 collector = token[4] = []; 是浅拷贝,因此 collector 值发生改变,会导致 token[4] 也会发生改变。
因此 sections 值变为如下:
sections = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9] ] ] ];
nestedTokens = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9] ] ] ];

i = 2;
token = ["name", ".", 9, 14];
token[0] = "name"; 因此 collector = [["text", " ", 8, 9],["name", ".", 9, 14]];
sections = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14] ] ] ];
nestedTokens = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14] ] ] ];
i = 3;
token = ["text", " * <div>", 14, 22];
token[0] = "text"; 
collector = [
  ["text", " ", 8, 9],
  ["name", ".", 9, 14],
  ["text", " * <div>", 14, 22]
];
sections = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22] ] ] ];

nestedTokens = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22] ] ] ];

i = 4;
token = ["name", "name", 22, 30];
token[0] = "name";
collector = [
  ["text", " ", 8, 9],
  ["name", ".", 9, 14],
  ["text", " * <div>", 14, 22],
  ["name", "name", 22, 30]
];

sections = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30] ] ] ];

nestedTokens = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30] ] ] ];

i = 5;
token = ["text", "</div> ", 30, 37];
token[0] = "text";
collector = [
  ["text", " ", 8, 9],
  ["name", ".", 9, 14],
  ["text", " * <div>", 14, 22],
  ["name", "name", 22, 30],
  ["text", "</div> ", 30, 37]
];

sections = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] ] ];

nestedTokens = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] ] ];

i = 6;
token = ['/', 'msg', 37, 45];
token[0] = '/';

此时此刻sections 和 nestedTokens 值如下:

sections = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] ] ];

nestedTokens = [ ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] ] ];

因此会进入如下代码:

case '/':
  section = sections.pop();
  section[5] = token[2];
  collector = sections.length > 0 ? sections[sections.length - 1][4] : nestedTokens;
  break;

如上代码执行完成后;

section = ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] ];
sections = [];
section[5] = token[2];

因此 section 值变为如下:

section = ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] , 37 ];

由于 sections.length = 0; 因此 把 nestedTokens 赋值给 collector; 
collector = nestedTokens;

最后返回的值:nestedTokens = [["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] , 37 ]];
          

因此 Writer.prototype.render 如下方法中的 第一个 this.parse() 函数就返回了值; 因此 tokens的值就是上面返回的值。

Writer.prototype.render = function render (template, view, partials, tags) {
    var tokens = this.parse(template, tags);
    var context = (view instanceof Context) ? view : new Context(view);
    return this.renderTokens(tokens, context, partials, template);
  };

现在我们要调用 new Context(view) 方法了。

Context 函数有如下方法:

/*
     @param {view} { "name": "kongzhi", "msg": ['111'] }
     @param {parentContext} undefined
    */
    function Context (view, parentContext) {
      this.view = view;
      this.cache = { '.': this.view };
      this.parent = parentContext;
    }
    Context.prototype.push = function push (view) {
      return new Context(view, this);
    };
    Context.prototype.lookup = function lookup (name) {};

因此 context.view = { "name": "kongzhi", "msg": ['111'] };
context.cache = { '.' : { "name": "kongzhi", "msg": ['111'] } };
context.parent = undefined;
context 实列除了上面列举的三个属性外,在原型上还有 push 和 lookup方法。

接下来就执行:this.renderTokens(tokens, context, partials, template); 代码;
如上参数:

tokens = [["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] , 37 ]];
    context = {
      view: { "name": "kongzhi", "msg": ['111'] },
      cache: { '.' : { "name": "kongzhi", "msg": ['111'] } },
      parent: undefined,
      __proto__: {
        push: fn,
        lookup: fn
      }
    };
partials = undefined;
template = "{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}";

现在我们继续来看下 renderTokens 函数,代码如下:

Writer.prototype.renderTokens = function renderTokens (tokens, context, partials, originalTemplate) {
      var buffer = '';
      var token, symbol, value;
      for (var i = 0, numTokens = tokens.length; i < numTokens; ++i) {
        value = undefined;
        token = tokens[i];
        symbol = token[0];

        if (symbol === '#') value = this.renderSection(token, context, partials, originalTemplate);
        else if (symbol === '^') value = this.renderInverted(token, context, partials, originalTemplate);
        else if (symbol === '>') value = this.renderPartial(token, context, partials, originalTemplate);
        else if (symbol === '&') value = this.unescapedValue(token, context);
        else if (symbol === 'name') value = this.escapedValue(token, context);
        else if (symbol === 'text') value = this.rawValue(token);
        if (value !== undefined)
          buffer += value;
      }
      return buffer;
 }

由上可知:tokens = [["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] , 37 ]];

因此循环tokens, 因此 token = tokens[i] = ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] , 37 ];

因此 symbol = "#"; 因此就调用 renderSection 函数,调用完成后,返回的值赋值给value值,因此下面我们来看下 renderSection 函数的代码如下所示:

/*
       * @param {token} 
       token = ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] , 37 ];
       * @param {context} 
        context = {
          view: { "name": "kongzhi", "msg": ['111'] },
          cache: { '.' : { "name": "kongzhi", "msg": ['111'] } },
          parent: undefined,
          __proto__: {
            push: fn,
            lookup: fn
          }
        };
       * @param {partials} 是否是可重用的模板,目前没有传递,值为undefined
       * @param {originalTemplate} 为页面模板 值为:"{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}";
      */
      Writer.prototype.renderSection = function renderSection (token, context, partials, originalTemplate) {
        var self = this;
        var buffer = '';
        var value = context.lookup(token[1]);

        // This function is used to render an arbitrary template
        // in the current context by higher-order sections.
        function subRender (template) {
          return self.render(template, context, partials);
        }
        if (!value) return;
        if (isArray(value)) {
          for (var j = 0, valueLength = value.length; j < valueLength; ++j) {
            buffer += this.renderTokens(token[4], context.push(value[j]), partials, originalTemplate);
          }
        } else if (typeof value === 'object' || typeof value === 'string' || typeof value === 'number') {
          buffer += this.renderTokens(token[4], context.push(value), partials, originalTemplate);
        } else if (isFunction(value)) {
          if (typeof originalTemplate !== 'string')
            throw new Error('Cannot use higher-order sections without the original template');

          // Extract the portion of the original template that the section contains.
          value = value.call(context.view, originalTemplate.slice(token[3], token[5]), subRender);

          if (value != null)
            buffer += value;
        } else {
          buffer += this.renderTokens(token[4], context, partials, originalTemplate);
        }
        return buffer;
      };

如上代码,首先会调用 var value = context.lookup(token[1]); lookup函数,然后把值赋值给 value. 那么此时传递的 token[1] = 'msg'; 因此我们下面先看下 context.lookup(token[1]) 函数,代码如下所示:

Context.prototype.lookup = function lookup (name) {
        var cache = this.cache;
        var value;
        if (cache.hasOwnProperty(name)) {
          value = cache[name];
        } else {
          var context = this, intermediateValue, names, index, lookupHit = false;
          while (context) {
            if (name.indexOf('.') > 0) {
              intermediateValue = context.view;
              names = name.split('.');
              index = 0;
              while (intermediateValue != null && index < names.length) {
                if (index === names.length - 1)
                  lookupHit = (
                    hasProperty(intermediateValue, names[index]) 
                    || primitiveHasOwnProperty(intermediateValue, names[index])
                  );
                intermediateValue = intermediateValue[names[index++]];
              }
            } else {
              intermediateValue = context.view[name];
              lookupHit = hasProperty(context.view, name);
            }
            if (lookupHit) {
              value = intermediateValue;
              break;
            }
            context = context.parent;
          }
          cache[name] = value;
        }
        if (isFunction(value))
          value = value.call(this.view);
        return value;
      };

如上函数参数 name 值为 = "msg";
var cache = this.cache; 我们之前保存的 this.cache 的值为 = { ".": {name: 'kongzhi', msg: ['111']}};
很明显 if (cache.hasOwnProperty(name)) {} 为false, 因此进入else语句了。
在else语句代码如下:
var context = this; 这里的this指向了 Context 对象。之前Context值如下所示:

Context = {
          view: { "name": "kongzhi", "msg": ['111'] },
          cache: { '.' : { "name": "kongzhi", "msg": ['111'] } },
          parent: undefined,
          __proto__: {
            push: fn,
            lookup: fn
          }
};

因此 context 也是这个值了。
执行while语句 判断 while(context) {}; 然后判断 if (name.indexOf('.') > 0) {} else {} 这样的,我们上面name为
字符串 "msg"; 因此进入else语句代码内部,intermediateValue = context.view[name]; 因此 intermediateValue = ['111']; lookupHit = hasProperty(context.view, name); 判断 context.view 对象内部是否有 "msg" 这个属性,因此lookupHit = true; 然后执行如下代码:

if (lookupHit) {
         value = intermediateValue;
         break;
 }

因此 value = ['111']; 跳出while循环,当然 如果 lookupHit 为false的话,它会通过递归的方式查找父级元素,直到最顶层
元素,从这句代码可以看到:context = context.parent; 最后跳出while循环后,执行下面的代码 cache[name] = value;
因此这个时候 this.cache = { ".": {"name": "kongzhi", "msg": ["111"]}, "msg": ["111"]};
最后判断,我们的 value 是否是个函数,如果是函数的话,就调用该函数执行。我们上面的demo就可以很好的列子,demo如下:

var data = {
         "name": "kongzhi",
         "msg": {
           "sex": " male ", 
           "age": "31",
           "marriage": 'single'
         },
         "wrapped": function() {
           return function(text, render) {
             return '<div>' + render(text) + '</div>'
           } 
         }
}
var tpl = `{{#wrapped}} {{name}} is men {{/wrapped}}`;
var html = Mustache.render(tpl, data); 
console.log(html); // 打印 <div> kongzhi is men </div>

代码: if (isFunction(value)) { value = value.call(this.view);} 我们demo如上,wrapped 就是一个函数,因此它会调用执行,其中 this.view 参数的值为 = { "name": "kongzhi", "msg": ["111"] }; wrapped函数它自身返回一个函数,它会把值赋值给value,因此把value返回回去。因此 又回到 Writer.prototype.renderSection 函数内部,该函数内部又会判断该value 是否是一个数组,如果是个数组的话,执行某些操作,或者 他是一个对象、一个数字、一个字符串、就执行另外一些操作,或者它是一个函数就调用该函数。如下 Writer.prototype.renderSection 函数代码可知:

Writer.prototype.renderSection = function renderSection (token, context, partials, originalTemplate) {
          var self = this;
          var buffer = '';
          var value = context.lookup(token[1]);

          // This function is used to render an arbitrary template
          // in the current context by higher-order sections.
          function subRender (template) {
            return self.render(template, context, partials);
          }
          if (!value) return;
          if (isArray(value)) {
            for (var j = 0, valueLength = value.length; j < valueLength; ++j) {
              buffer += this.renderTokens(token[4], context.push(value[j]), partials, originalTemplate);
            }
          } else if (typeof value === 'object' || typeof value === 'string' || typeof value === 'number') {
            buffer += this.renderTokens(token[4], context.push(value), partials, originalTemplate);
          } else if (isFunction(value)) {
            if (typeof originalTemplate !== 'string')
              throw new Error('Cannot use higher-order sections without the original template');

            // Extract the portion of the original template that the section contains.
            value = value.call(context.view, originalTemplate.slice(token[3], token[5]), subRender);

            if (value != null)
              buffer += value;
          } else {
            buffer += this.renderTokens(token[4], context, partials, originalTemplate);
          }
          return buffer;
        }

因此 我们上面 value 返回的是 = ['111']; 他是一个数组。因此会进入第一个if语句代码内部。因此循环该数组,由于该 value
数组里面只有 ['111'] 这样的,因此就循环1次,会执行如下代码:
buffer += this.renderTokens(token[4], context.push(value[j]), partials, originalTemplate);

在调用该函数之前,会调用 context.push 函数,代码如下:

function Context (view, parentContext) {
     this.view = view;
     this.cache = { '.': this.view };
     this.parent = parentContext;
 }
 Context.prototype.push = function push (view) {
      return new Context(view, this);
  };

这里的this就是我们之前的 context对象了。因此此时的 context对象就变为如下值:

context = {
     view: '111',
      cache: {".": "111"},
      parent: {
          parent: undefined,
          view: {
             "name": "kongzhi",
              "msg": ["111"]
           },
          cache: {
            "msg": ["111"],
              ".": {
                "name": "kongzhi",
                "msg": ["111"]
              }
            }
          }
 };

我们之前的token值如下:

token = ["#", "msg", 0, 8, [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ] , 37 ];


因此调用 buffer += this.renderTokens(token[4], context.push(value[j]), partials, originalTemplate);

Writer.prototype.renderTokens = function renderTokens (tokens, context, partials, originalTemplate) {
          var buffer = '';
          var token, symbol, value;
          for (var i = 0, numTokens = tokens.length; i < numTokens; ++i) {
            value = undefined;
            token = tokens[i];
            symbol = token[0];

            if (symbol === '#') value = this.renderSection(token, context, partials, originalTemplate);
            else if (symbol === '^') value = this.renderInverted(token, context, partials, originalTemplate);
            else if (symbol === '>') value = this.renderPartial(token, context, partials, originalTemplate);
            else if (symbol === '&') value = this.unescapedValue(token, context);
            else if (symbol === 'name') value = this.escapedValue(token, context);
            else if (symbol === 'text') value = this.rawValue(token);

            if (value !== undefined)
              buffer += value;
          }

          return buffer;
        }

继续递归调用该函数,那么 token[4] = [ ["text", " ", 8, 9], ["name", ".", 9, 14], ["text", " * <div>", 14, 22], ["name", "name", 22, 30], ["text", "</div> ", 30, 37] ];

context 值就是我们上面的值;
partials: 可重用的模板,目前没有传递给参数,因此为undefined。
originalTemplate: 就是我们的模板,值为:"{{#msg}} {{.}} * <div>{{name}}</div> {{/msg}}";

如上我们把token[4] 作为参数传递进去,因此会循环该数组,然后 tokens[][0] === 'text' 只有该数组内的第一项,第三项,
第五项,当 tokens[i][0] === 'name'; 只有数组中的第二项和第四项。我们来分别来看下代码如何执行的;

1. 第一个数组值为:["text", " ", 8, 9]; 因此:value = this.rawValue(["text", " ", 8, 9]); rawValue 函数代码如下:

Writer.prototype.rawValue = function rawValue (token) {
return token[1];
};

该函数直接 返回 token[1]; 因此 value = " "; 因此第一次循环 buffer = " ";

2. 第二个数组值为:["name", ".", 9, 14]; 因此 value = this.escapedValue(token, context); escapedValue 函数代码:

/*
         @param {token} ["name", ".", 9, 14]
         @param {context}
         context = {
            view: '111',
            cache: {".": "111"},
            parent: {
              parent: undefined,
              view: {
                "name": "kongzhi",
                "msg": ["111"]
              },
              cache: {
                "msg": ["111"],
                ".": {
                  "name": "kongzhi",
                  "msg": ["111"]
                }
              }
            }
         };
        */
        Writer.prototype.escapedValue = function escapedValue (token, context) {
          var value = context.lookup(token[1]);
          if (value != null)
            return mustache.escape(value);
        };
        Context.prototype.lookup = function lookup (name) {
          var cache = this.cache;
          var value;
          if (cache.hasOwnProperty(name)) {
            value = cache[name];
          } else {
          }
          // ....
          return value;
        }

如上代码可以看到,我们的token[1] = '.'; 因此先调用 Context.prototype.lookup 这个方法,该方法内部的this指向了
context 对象,我们可以从上面分析可以知道 context对象有哪些值了。因此 this.cache = context.cache = {".": "111"};
因此 if (cache.hasOwnProperty(name)) {} 条件为true,因此 value = cache[name]; 即:value = "111";
最后返回 Writer.prototype.escapedValue 函数内部代码,
if (value != null) {
return mustache.escape(value);
};
从源码当中我们知道:

var entityMap = {
          '&': '&amp;',
          '<': '&lt;',
          '>': '&gt;',
          '"': '&quot;',
          "'": '&#39;',
          '/': '&#x2F;',
          '`': '&#x60;',
          '=': '&#x3D;'
        };
        mustache.escape = escapeHtml;
        function escapeHtml (string) {
          return String(string).replace(/[&<>"'`=\/]/g, function fromEntityMap (s) {
            return entityMap[s];
          });
        }

最后就会返回一个字符串,从该代码中,我们也可以看到,如果模板中有 <a> 这样类似的标签的时候,它会转换成 "&lt;a&gt;" 这样
的,会对html标签进行转义操作。因此这里我们的值 value 就返回字符串 "111" 了。 buffer = " " + "111" 因此 最后 buffer = " 111";

3. 第三个数组为:["text", " * <div>", 14, 22]; 因此:value = this.rawValue(["text", " * <div>", 14, 22]); rawValue 函数代码如下:
Writer.prototype.rawValue = function rawValue (token) {
return token[1];
};
因此 value = " * <div>";
最后 buffer = " 111 * <div>";

4. 第四个数组为:["name", "name", 22, 30]; 因此 value = this.escapedValue(token, context); 步骤和第二步一样的。
escapedValue 函数代码(为了方便查看,继续贴下代码):

/*
         @param {token} ["name", "name", 22, 30]
         @param {context}
         context = {
            view: '111',
            cache: {".": "111"},
            parent: {
              parent: undefined,
              view: {
                "name": "kongzhi",
                "msg": ["111"]
              },
              cache: {
                "msg": ["111"],
                ".": {
                  "name": "kongzhi",
                  "msg": ["111"]
                }
              }
            }
         };
        */
        Writer.prototype.escapedValue = function escapedValue (token, context) {
          var value = context.lookup(token[1]);
          if (value != null)
            return mustache.escape(value);
        };
        Context.prototype.lookup = function lookup (name) {
          var cache = this.cache;
          var value;
          if (cache.hasOwnProperty(name)) {
            value = cache[name];
          } else {
            var context = this, intermediateValue, names, index, lookupHit = false;
            while (context) {
              if (name.indexOf('.') > 0) {
                // ... 代码省略
              } else {
                intermediateValue = context.view[name];
                lookupHit = hasProperty(context.view, name);
              }
              if (lookupHit) {
                value = intermediateValue;
                break;
              }
              context = context.parent;
            }
            cache[name] = value;
          }
          // ....
          return value;
        }

如上代码,执行 var value = context.lookup(token[1]); 因此 token[1] = "name"; 由上可知:cache = {".": "111"};
因此代码会执行else代码内部;进入 while循环内部,if (name.indexOf('.') > 0) {} 判断 "name" 是否能找到 ".", 这里是找不到的,因此又进去else代码内部。因此 intermediateValue = context.view[name] = context.view["name"]; 由上面的context的值我们可知,context.view = "111"; 因此 intermediateValue = undefined; 找不到该值;同理 lookupHit = false; 因此 context = context.parent; 查找父级元素,依次类推.... 由上面可知,我们知道 context的值了, 继续看下context 值吧,如下所示:

context = {
          view: '111',
          cache: {".": "111"},
          parent: {
            parent: undefined,
            view: {
              "name": "kongzhi",
              "msg": ["111"]
            },
            cache: {
              "msg": ["111"],
              ".": {
                "name": "kongzhi",
                "msg": ["111"]
              }
            }
          }
 };

我们执行 context = context.parent; 它是有的,因此会继续进入下一次while循环代码,因此此时的context值就变为如下了:

context = {
          parent: undefined,
          view: {
            "name": "kongzhi",
            "msg": ["111"]
          },
          cache: {
            "msg": ["111"],
            ".": {
              "name": "kongzhi",
              "msg": ["111"]
            }
          }
        }

和上面的操作一样,也会进入else语句代码内,现在需要执行如下代码:
intermediateValue = context.view[name]; lookupHit = hasProperty(context.view, name);
因此 intermediateValue = context.view["name"] = "kongzhi"; lookupHit = true; 因此会执行如下代码:

if (lookupHit) {
      value = intermediateValue;
      break;
 }

最后我们的 value = "kongzhi" 了,使用break语句,跳出while循环,如上可以看到,如果我们这一次又没有找到该值的话,它还会继续往它的父级元素上面的递归查找是否有该值,如果有直到找到为止,否则的话,就找不到。直接返回 name 这个未解析的变量。
跳出while循环后,就执行 cache[name] = value; 因此这个时候 cache 的值变为如下:

cache = {
          ".": 111,
          "name": "kongzhi"
        }

此时此刻,我们全局的context的值就变为如下了:

context = {
          view: '111',
          cache: {".": "111", "name": "kongzhi"},
          parent: {
            parent: undefined,
            view: {
              "name": "kongzhi",
              "msg": ["111"]
            },
            cache: {
              "msg": ["111"],
              ".": {
                "name": "kongzhi",
                "msg": ["111"]
              }
            }
          }
};

下面还有如下代码需要执行:

if (isFunction(value))
     value = value.call(this.view);
    return value;

如上,如果该value是一个函数的话,就会返回一个函数给value;否则的话,直接把值value返回给回去。因此我们需要跳到Writer.prototype.escapedValue 函数中,如下代码:

Writer.prototype.escapedValue = function escapedValue (token, context) {
     var value = context.lookup(token[1]);
     if (value != null)
          return mustache.escape(value);
 };

返回回来的value = "kongzhi"; 因此会调用 mustache.escape(value); 函数返回回去,escape 函数我们之前讲过,它是对html标签进行转义的,因此这里为了节约篇幅,就不贴代码了。执行完成后,把值返回回去。因此我们现在又需要跳到Writer.prototype.renderTokens 函数中,再看剩下的代码了,为了查看方便,我继续贴下该函数代码:

Writer.prototype.renderTokens = function renderTokens (tokens, context, partials, originalTemplate) {
          var buffer = '';
          var token, symbol, value;
          for (var i = 0, numTokens = tokens.length; i < numTokens; ++i) {
            value = undefined;
            token = tokens[i];
            symbol = token[0];

            if (symbol === '#') value = this.renderSection(token, context, partials, originalTemplate);
            else if (symbol === '^') value = this.renderInverted(token, context, partials, originalTemplate);
            else if (symbol === '>') value = this.renderPartial(token, context, partials, originalTemplate);
            else if (symbol === '&') value = this.unescapedValue(token, context);
            else if (symbol === 'name') value = this.escapedValue(token, context);
            else if (symbol === 'text') value = this.rawValue(token);
            if (value !== undefined)
              buffer += value;
          }
          return buffer;
 }

因此 执行下面代码 if (value !== undefined) { buffer += value; } 代码了,从上面第三步我们知道 buffer的值了。
buffer = " 111 * <div>"; 因此我们继续字符串拼接,buffer += value; 因此 buffer = " 111 * <div>kongzhi";

5. 第五个数组为:token = ["text", "</div> ", 30, 37]; 由于 token[0] = "text"; 因此:value = this.rawValue(["text", " * <div>", 14, 22]); rawValue 函数代码如下:

Writer.prototype.rawValue = function rawValue (token) {
return token[1];
};
因此 value = "</div> "; 最后我们又判断 if (value !== undefined) { buffer += value; }; 在第四步我们知道
buffer的值 = " 111 * <div>kongzhi"; 因此 该值继续和 "</div> " 字符串拼接的话,最后我们的buffer值就为如下了:

buffer = " 111 * <div>kongzhi</div> ";

如上就是整个模板的解析的过程。当然 mustache.js 里面还有很多未讲解到的代码,比如兼容到一些其他的情况。比如在:
Writer.prototype.renderTokens 函数中,还有如下:

if (symbol === '#') value = this.renderSection(token, context, partials, originalTemplate);
else if (symbol === '^') value = this.renderInverted(token, context, partials, originalTemplate);
else if (symbol === '>') value = this.renderPartial(token, context, partials, originalTemplate);
else if (symbol === '&') value = this.unescapedValue(token, context);
else if (symbol === 'name') value = this.escapedValue(token, context);
else if (symbol === 'text') value = this.rawValue(token);

如上我们还有三个函数没有讲解到,比如 symbol === '^' 需要调用 this.renderInverted()函数,symbol === '>' 需要调用this.renderPartial()函数,symbol === '&' 需要调用 this.unescapedValue() 这个函数。我们可以贴下他们的代码如下:

Writer.prototype.renderInverted = function renderInverted (token, context, partials, originalTemplate) {
     var value = context.lookup(token[1]);
     // Use JavaScript's definition of falsy. Include empty arrays.
     // See https://github.com/janl/mustache.js/issues/186
     if (!value || (isArray(value) && value.length === 0))
          return this.renderTokens(token[4], context, partials, originalTemplate);
 };

 Writer.prototype.renderPartial = function renderPartial (token, context, partials) {
      if (!partials) return;
      var value = isFunction(partials) ? partials(token[1]) : partials[token[1]];
       if (value != null)
            return this.renderTokens(this.parse(value), context, partials, value);
 };

Writer.prototype.unescapedValue = function unescapedValue (token, context) {
     var value = context.lookup(token[1]);
     if (value != null)
        return value;
 };

如上代码原理也是一样的,这里就不做一一分析了,觉得有意思的,可以自己分析下。到这里源码是分析完了。我们可以从头一步步去理解下mustache.js 模板引擎如何解析的思路。