Backbone的localStorage.js源码详细分析
Backbone.localStorage.js是将数据存储到游览器客户端本地的（当没有服务器的情况下）
地址：https://github.com/jeromegn/Backbone.localStorage
1 整个函数是一个自执行函数，简化版形式如下
(function(a,fn) {
//...
})(a,fn);
2 9-12行/**---------此处是判断上下文有没有引入AMD模块（如requirejs）-----------*/
if(typeofdefine==="function"&&define.amd) {
// AMD. Register as an anonymous module.
define(["underscore","backbone"],function(_, Backbone) {
// Use global variables if the locals are undefined.
returnfactory(_ || root._, Backbone || root.Backbone);
});
}else{
// RequireJS isn't being used. Assume underscore and backbone are loaded in script tags
factory(_,Backbone);
}
此种判断方法比较常见，类似的如 toastr.js种
typeofdefine==='function'&&define.amd?define:function(deps, factory) {
if(typeofmodule!=='undefined'&&module.exports) {//Node
module.exports= factory(require('jquery'));
}else{
window['toastr'] = factory(window['jQuery']);
}
}
/** * Backbone localStorage Adapter * Version 1.1.0 * * https://github.com/jeromegn/Backbone.localStorage */ (function (root, factory) { /**---------此处是判断上下文有没有引入AMD模块（如requirejs）-----------*/ if (typeof define === "function" && define.amd) { // AMD. Register as an anonymous module. define(["underscore","backbone"], function(_, Backbone) { // Use global variables if the locals are undefined. return factory(_ || root._, Backbone || root.Backbone); }); } else { // RequireJS isn't being used. Assume underscore and backbone are loaded in script tags factory(_, Backbone); } }(this, function(_, Backbone) { // A simple module to replace `Backbone.sync` with *localStorage*-based // persistence. Models are given GUIDS, and saved into a JSON object. Simple // as that. // Hold reference to Underscore.js and Backbone.js in the closure in order // to make things work even if they are removed from the global namespace // Generate four random hex digits. function S4() { return (((1+Math.random())*0x10000)|0).toString(16).substring(1); }; // Generate a pseudo-GUID by concatenating random hexadecimal. // /**---------此处生成随机数 如 d9ab5797-9773-9bcd-27b1-9f23a3170957-----------*/ function guid() { return (S4()+S4()+"-"+S4()+"-"+S4()+"-"+S4()+"-"+S4()+S4()+S4()); }; // Our Store is represented by a single JS object in *localStorage*. Create it // with a meaningful name, like the name you'd give a table. // window.Store is deprecated, use Backbone.LocalStorage instead /**---------定义LocalStorage函数-----------*/ Backbone.LocalStorage = window.Store = function(name) { this.name = name; var store = this.localStorage().getItem(this.name); this.records = (store && store.split(",")) || []; }; /**---------扩展LocalStorage函数 的 增删改查 等其他方法-----------*/ _.extend(Backbone.LocalStorage.prototype, { // Save the current state of the **Store** to *localStorage*. save: function() { this.localStorage().setItem(this.name, this.records.join(",")); }, // Add a model, giving it a (hopefully)-unique GUID, if it doesn't already // have an id of it's own. create: function(model) { if (!model.id) { model.id = guid();//生成唯一id model.set(model.idAttribute, model.id);//给模型添加一条新属性id } this.localStorage().setItem(this.name+"-"+model.id, JSON.stringify(model));//setItem为原生localstorage的方法，此处是真正的把数据存储到客户端 this.records.push(model.id.toString()); this.save(); return this.find(model); }, // Update a model by replacing its copy in `this.data`. update: function(model) { this.localStorage().setItem(this.name+"-"+model.id, JSON.stringify(model)); if (!_.include(this.records, model.id.toString())) this.records.push(model.id.toString()); this.save(); return this.find(model); }, // Retrieve a model from `this.data` by id. find: function(model) { return this.jsonData(this.localStorage().getItem(this.name+"-"+model.id)); }, // Return the array of all models currently in storage. findAll: function() { return _(this.records).chain() .map(function(id){ return this.jsonData(this.localStorage().getItem(this.name+"-"+id)); }, this) .compact() .value(); }, // Delete a model from `this.data`, returning it. destroy: function(model) { if (model.isNew()) return false this.localStorage().removeItem(this.name+"-"+model.id); this.records = _.reject(this.records, function(id){ return id === model.id.toString(); }); this.save(); return model; }, localStorage: function() { return localStorage;//返回原生的localStorage }, // fix for "illegal access" error on Android when JSON.parse is passed null jsonData: function (data) { return data && JSON.parse(data); } }); // localSync delegate to the model or collection's // *localStorage* property, which should be an instance of `Store`. // window.Store.sync and Backbone.localSync is deprectated, use Backbone.LocalStorage.sync instead Backbone.LocalStorage.sync = window.Store.sync = Backbone.localSync = function(method, model, options) { var store = model.localStorage || model.collection.localStorage; var resp, errorMessage, syncDfd = $.Deferred && $.Deferred(); //If $ is having Deferred - use it.//生成query的Deferred对象 //此处是一个较大的知识点，就是promise规范，和jquery的deferred 和promise 此处不展开 try { switch (method) { case "read": resp = model.id != undefined ? store.find(model) : store.findAll(); break; case "create": resp = store.create(model); break; case "update": resp = store.update(model); break; case "delete": resp = store.destroy(model); break; } } catch(error) { if (error.code === DOMException.QUOTA_EXCEEDED_ERR && window.localStorage.length === 0) errorMessage = "Private browsing is unsupported"; else errorMessage = error.message; } if (resp) { model.trigger("sync", model, resp, options); if (options && options.success) options.success(resp); if (syncDfd) syncDfd.resolve(resp);//回掉状态改为成功 } else { errorMessage = errorMessage ? errorMessage : "Record Not Found"; if (options && options.error) options.error(errorMessage); if (syncDfd) syncDfd.reject(errorMessage);//回掉状态改为失败 } // add compatibility with $.ajax // always execute callback for success and error if (options && options.complete) options.complete(resp); return syncDfd && syncDfd.promise(); }; /**---------保存原来的sync-----------*/ Backbone.ajaxSync = Backbone.sync; /**---------此处来判断返回哪个函数，用localstorage还是发送ajax-----------*/ Backbone.getSyncMethod = function(model) { if(model.localStorage || (model.collection && model.collection.localStorage)) { return Backbone.localSync; } return Backbone.ajaxSync; }; // Override 'Backbone.sync' to default to localSync, // the original 'Backbone.sync' is still available in 'Backbone.ajaxSync' /**---------覆盖Backbone的sync，因为原来的已经保存-----------*/ Backbone.sync = function(method, model, options) { return Backbone.getSyncMethod(model).apply(this, [method, model, options]); //注意：Backbone.getSyncMethod(model)返回的是一个函数，再apply(),才执行返回的这个函数 }; return Backbone.LocalStorage; }));
