_.invokeMap(collection, path, [args])

79

_.invokeMap(collection, path, [args])

引用path参数对应的方法处理collection中的每一个元素，将引用方法处理后的结果组成一个数组返回。

任何额外的参数都被传递给每一次引用方法的调用

如果path参数是一个方法，直接调用，如果不是，就是路径数组或者路径字符串，就去那个路径下寻找对应的方法

调用引用方法的时候this被绑定到collection的每一个元素上

参数

collection (Array|Object): 需要遍历的集合
path (Array|Function|string): 遍历每个元素调用的方法或者那个方法的路径
[args] (...*): 每一次调用方法的额外参数

返回值

(Array): 返回结果数组

例子

 

_.invokeMap([[5, 1, 7], [3, 2, 1]], 'sort');
// => [[1, 5, 7], [1, 2, 3]]
 
_.invokeMap([123, 456], String.prototype.split, '');
// => [['1', '2', '3'], ['4', '5', '6']]

 

源代码：

/**
 * lodash (Custom Build) <https://lodash.com/>
 * Build: `lodash modularize exports="npm" -o ./`
 * Copyright jQuery Foundation and other contributors <https://jquery.org/>
 * Released under MIT license <https://lodash.com/license>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 */

/** Used as the `TypeError` message for "Functions" methods. */
var FUNC_ERROR_TEXT = 'Expected a function';

/** Used to stand-in for `undefined` hash values. */
var HASH_UNDEFINED = '__lodash_hash_undefined__';

/** Used as references for various `Number` constants. */
var INFINITY = 1 / 0,
    MAX_SAFE_INTEGER = 9007199254740991;

/** `Object#toString` result references. */
var argsTag = '[object Arguments]',
    funcTag = '[object Function]',
    genTag = '[object GeneratorFunction]',
    symbolTag = '[object Symbol]';

/** Used to match property names within property paths. */
var reIsDeepProp = /\.|\[(?:[^[\]]*|(["'])(?:(?!\1)[^\\]|\\.)*?\1)\]/,
    reIsPlainProp = /^\w*$/,
    reLeadingDot = /^\./,
    rePropName = /[^.[\]]+|\[(?:(-?\d+(?:\.\d+)?)|(["'])((?:(?!\2)[^\\]|\\.)*?)\2)\]|(?=(?:\.|\[\])(?:\.|\[\]|$))/g;

/**
 * Used to match `RegExp`
 * [syntax characters](http://ecma-international.org/ecma-262/7.0/#sec-patterns).
 */
var reRegExpChar = /[\\^$.*+?()[\]{}|]/g;

/** Used to match backslashes in property paths. */
var reEscapeChar = /\\(\\)?/g;

/** Used to detect host constructors (Safari). */
var reIsHostCtor = /^\[object .+?Constructor\]$/;

/** Used to detect unsigned integer values. */
var reIsUint = /^(?:0|[1-9]\d*)$/;

/** Detect free variable `global` from Node.js. */
var freeGlobal = typeof global == 'object' && global && global.Object === Object && global;

/** Detect free variable `self`. */
var freeSelf = typeof self == 'object' && self && self.Object === Object && self;

/** Used as a reference to the global object. */
var root = freeGlobal || freeSelf || Function('return this')();

/**
 * A faster alternative to `Function#apply`, this function invokes `func`
 * with the `this` binding of `thisArg` and the arguments of `args`.
 *
 * @private
 * @param {Function} func The function to invoke.
 * @param {*} thisArg The `this` binding of `func`.
 * @param {Array} args The arguments to invoke `func` with.
 * @returns {*} Returns the result of `func`.
 */
//一个更快的apply方法
function apply(func, thisArg, args) {
  switch (args.length) {
    case 0: return func.call(thisArg);
    case 1: return func.call(thisArg, args[0]);
    case 2: return func.call(thisArg, args[0], args[1]);
    case 3: return func.call(thisArg, args[0], args[1], args[2]);
  }
  return func.apply(thisArg, args);
}

/**
 * The base implementation of `_.times` without support for iteratee shorthands
 * or max array length checks.
 *
 * @private
 * @param {number} n The number of times to invoke `iteratee`.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {Array} Returns the array of results.
 */
//_.times的基础实现，循环n次，返回iteratee处理的index组成的数组
function baseTimes(n, iteratee) {
  var index = -1,//循环索引
      result = Array(n);//结果数组，长度为n

  while (++index < n) {//循环n次，结果数组每一个元素是当前index被iteratee处理后的结果
    result[index] = iteratee(index);
  }
  return result;
}

/**
 * Gets the value at `key` of `object`.
 *
 * @private
 * @param {Object} [object] The object to query.
 * @param {string} key The key of the property to get.
 * @returns {*} Returns the property value.
 */
//获取object上对应key的值
function getValue(object, key) {
  return object == null ? undefined : object[key];
}

/**
 * Checks if `value` is a host object in IE < 9.
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a host object, else `false`.
 */
//判断value是否是一个宿主对象，在IE9以下的浏览器中
function isHostObject(value) {
  // Many host objects are `Object` objects that can coerce to strings
  // despite having improperly defined `toString` methods.
  //很多宿主对象可以强制转成字符串尽管有一个不正确的toString方法
  var result = false;
  if (value != null && typeof value.toString != 'function') {
    try {
      result = !!(value + '');
    } catch (e) {}
  }
  return result;
}

/**
 * Creates a unary function that invokes `func` with its argument transformed.
 *
 * @private
 * @param {Function} func The function to wrap.
 * @param {Function} transform The argument transform.
 * @returns {Function} Returns the new function.
 */
//创建一个只有一个参数的函数，引用func来处理，这个函数的参数会被transform处理
function overArg(func, transform) {
  return function(arg) {
    return func(transform(arg));
  };
}

/** Used for built-in method references. */
var arrayProto = Array.prototype,
    funcProto = Function.prototype,
    objectProto = Object.prototype;

/** Used to detect overreaching core-js shims. */
var coreJsData = root['__core-js_shared__'];

/** Used to detect methods masquerading as native. */
var maskSrcKey = (function() {
  var uid = /[^.]+$/.exec(coreJsData && coreJsData.keys && coreJsData.keys.IE_PROTO || '');
  return uid ? ('Symbol(src)_1.' + uid) : '';
}());

/** Used to resolve the decompiled source of functions. */
var funcToString = funcProto.toString;

/** Used to check objects for own properties. */
var hasOwnProperty = objectProto.hasOwnProperty;

/**
 * Used to resolve the
 * [`toStringTag`](http://ecma-international.org/ecma-262/7.0/#sec-object.prototype.tostring)
 * of values.
 */
var objectToString = objectProto.toString;

/** Used to detect if a method is native. */
var reIsNative = RegExp('^' +
  funcToString.call(hasOwnProperty).replace(reRegExpChar, '\\$&')
  .replace(/hasOwnProperty|(function).*?(?=\\\()| for .+?(?=\\\])/g, '$1.*?') + '$'
);

/** Built-in value references. */
var Symbol = root.Symbol,
    propertyIsEnumerable = objectProto.propertyIsEnumerable,
    splice = arrayProto.splice;

/* Built-in method references for those with the same name as other `lodash` methods. */
var nativeKeys = overArg(Object.keys, Object),
    nativeMax = Math.max;

/* Built-in method references that are verified to be native. */
var Map = getNative(root, 'Map'),
    nativeCreate = getNative(Object, 'create');

/** Used to convert symbols to primitives and strings. */
var symbolProto = Symbol ? Symbol.prototype : undefined,
    symbolToString = symbolProto ? symbolProto.toString : undefined;

/**
 * Creates a hash object.
 *
 * @private
 * @constructor
 * @param {Array} [entries] The key-value pairs to cache.
 */
function Hash(entries) {
  var index = -1,
      length = entries ? entries.length : 0;

  this.clear();
  while (++index < length) {
    var entry = entries[index];
    this.set(entry[0], entry[1]);
  }
}

/**
 * Removes all key-value entries from the hash.
 *
 * @private
 * @name clear
 * @memberOf Hash
 */
function hashClear() {
  this.__data__ = nativeCreate ? nativeCreate(null) : {};
}

/**
 * Removes `key` and its value from the hash.
 *
 * @private
 * @name delete
 * @memberOf Hash
 * @param {Object} hash The hash to modify.
 * @param {string} key The key of the value to remove.
 * @returns {boolean} Returns `true` if the entry was removed, else `false`.
 */
function hashDelete(key) {
  return this.has(key) && delete this.__data__[key];
}

/**
 * Gets the hash value for `key`.
 *
 * @private
 * @name get
 * @memberOf Hash
 * @param {string} key The key of the value to get.
 * @returns {*} Returns the entry value.
 */
function hashGet(key) {
  var data = this.__data__;
  if (nativeCreate) {
    var result = data[key];
    return result === HASH_UNDEFINED ? undefined : result;
  }
  return hasOwnProperty.call(data, key) ? data[key] : undefined;
}

/**
 * Checks if a hash value for `key` exists.
 *
 * @private
 * @name has
 * @memberOf Hash
 * @param {string} key The key of the entry to check.
 * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
 */
function hashHas(key) {
  var data = this.__data__;
  return nativeCreate ? data[key] !== undefined : hasOwnProperty.call(data, key);
}

/**
 * Sets the hash `key` to `value`.
 *
 * @private
 * @name set
 * @memberOf Hash
 * @param {string} key The key of the value to set.
 * @param {*} value The value to set.
 * @returns {Object} Returns the hash instance.
 */
function hashSet(key, value) {
  var data = this.__data__;
  data[key] = (nativeCreate && value === undefined) ? HASH_UNDEFINED : value;
  return this;
}

// Add methods to `Hash`.
Hash.prototype.clear = hashClear;
Hash.prototype['delete'] = hashDelete;
Hash.prototype.get = hashGet;
Hash.prototype.has = hashHas;
Hash.prototype.set = hashSet;

/**
 * Creates an list cache object.
 *
 * @private
 * @constructor
 * @param {Array} [entries] The key-value pairs to cache.
 */
function ListCache(entries) {
  var index = -1,
      length = entries ? entries.length : 0;

  this.clear();
  while (++index < length) {
    var entry = entries[index];
    this.set(entry[0], entry[1]);
  }
}

/**
 * Removes all key-value entries from the list cache.
 *
 * @private
 * @name clear
 * @memberOf ListCache
 */
function listCacheClear() {
  this.__data__ = [];
}

/**
 * Removes `key` and its value from the list cache.
 *
 * @private
 * @name delete
 * @memberOf ListCache
 * @param {string} key The key of the value to remove.
 * @returns {boolean} Returns `true` if the entry was removed, else `false`.
 */
function listCacheDelete(key) {
  var data = this.__data__,
      index = assocIndexOf(data, key);

  if (index < 0) {
    return false;
  }
  var lastIndex = data.length - 1;
  if (index == lastIndex) {
    data.pop();
  } else {
    splice.call(data, index, 1);
  }
  return true;
}

/**
 * Gets the list cache value for `key`.
 *
 * @private
 * @name get
 * @memberOf ListCache
 * @param {string} key The key of the value to get.
 * @returns {*} Returns the entry value.
 */
function listCacheGet(key) {
  var data = this.__data__,
      index = assocIndexOf(data, key);

  return index < 0 ? undefined : data[index][1];
}

/**
 * Checks if a list cache value for `key` exists.
 *
 * @private
 * @name has
 * @memberOf ListCache
 * @param {string} key The key of the entry to check.
 * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
 */
function listCacheHas(key) {
  return assocIndexOf(this.__data__, key) > -1;
}

/**
 * Sets the list cache `key` to `value`.
 *
 * @private
 * @name set
 * @memberOf ListCache
 * @param {string} key The key of the value to set.
 * @param {*} value The value to set.
 * @returns {Object} Returns the list cache instance.
 */
function listCacheSet(key, value) {
  var data = this.__data__,
      index = assocIndexOf(data, key);

  if (index < 0) {
    data.push([key, value]);
  } else {
    data[index][1] = value;
  }
  return this;
}

// Add methods to `ListCache`.
ListCache.prototype.clear = listCacheClear;
ListCache.prototype['delete'] = listCacheDelete;
ListCache.prototype.get = listCacheGet;
ListCache.prototype.has = listCacheHas;
ListCache.prototype.set = listCacheSet;

/**
 * Creates a map cache object to store key-value pairs.
 *
 * @private
 * @constructor
 * @param {Array} [entries] The key-value pairs to cache.
 */
function MapCache(entries) {
  var index = -1,
      length = entries ? entries.length : 0;

  this.clear();
  while (++index < length) {
    var entry = entries[index];
    this.set(entry[0], entry[1]);
  }
}

/**
 * Removes all key-value entries from the map.
 *
 * @private
 * @name clear
 * @memberOf MapCache
 */
function mapCacheClear() {
  this.__data__ = {
    'hash': new Hash,
    'map': new (Map || ListCache),
    'string': new Hash
  };
}

/**
 * Removes `key` and its value from the map.
 *
 * @private
 * @name delete
 * @memberOf MapCache
 * @param {string} key The key of the value to remove.
 * @returns {boolean} Returns `true` if the entry was removed, else `false`.
 */
function mapCacheDelete(key) {
  return getMapData(this, key)['delete'](key);
}

/**
 * Gets the map value for `key`.
 *
 * @private
 * @name get
 * @memberOf MapCache
 * @param {string} key The key of the value to get.
 * @returns {*} Returns the entry value.
 */
function mapCacheGet(key) {
  return getMapData(this, key).get(key);
}

/**
 * Checks if a map value for `key` exists.
 *
 * @private
 * @name has
 * @memberOf MapCache
 * @param {string} key The key of the entry to check.
 * @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
 */
function mapCacheHas(key) {
  return getMapData(this, key).has(key);
}

/**
 * Sets the map `key` to `value`.
 *
 * @private
 * @name set
 * @memberOf MapCache
 * @param {string} key The key of the value to set.
 * @param {*} value The value to set.
 * @returns {Object} Returns the map cache instance.
 */
function mapCacheSet(key, value) {
  getMapData(this, key).set(key, value);
  return this;
}

// Add methods to `MapCache`.
MapCache.prototype.clear = mapCacheClear;
MapCache.prototype['delete'] = mapCacheDelete;
MapCache.prototype.get = mapCacheGet;
MapCache.prototype.has = mapCacheHas;
MapCache.prototype.set = mapCacheSet;

/**
 * Creates an array of the enumerable property names of the array-like `value`.
 *
 * @private
 * @param {*} value The value to query.
 * @param {boolean} inherited Specify returning inherited property names.
 * @returns {Array} Returns the array of property names.
 */
//创建一个array-like对象的可枚举的属性名组成的数组
//inherited布尔值，是否指定需要返回继承来的属性
function arrayLikeKeys(value, inherited) {
  // Safari 8.1 makes `arguments.callee` enumerable in strict mode.
  // Safari 9 makes `arguments.length` enumerable in strict mode.
  var result = (isArray(value) || isArguments(value))
    ? baseTimes(value.length, String)
    : [];
    //结果数组初始化，如果value是数组或者arguments对象，使用baseTimes处理，baseTimes返回的数组的元素是索引的字符串值组成的数组，否则为空数组

  var length = result.length,//结果数组长度
      skipIndexes = !!length;//是否需要跳过数字索引

  for (var key in value) {//for in循环value的可枚举属性
    if ((inherited || hasOwnProperty.call(value, key)) &&
        !(skipIndexes && (key == 'length' || isIndex(key, length)))) {
      //如果需要返回继承来的属性值，或者当前key是value自身属性
      //并且判断是否是不是length属性或者数字索引属性，因为这两种属性需要跳过
      result.push(key);
    }
  }
  return result;
}

/**
 * Gets the index at which the `key` is found in `array` of key-value pairs.
 *
 * @private
 * @param {Array} array The array to inspect.
 * @param {*} key The key to search for.
 * @returns {number} Returns the index of the matched value, else `-1`.
 */
function assocIndexOf(array, key) {
  var length = array.length;
  while (length--) {
    if (eq(array[length][0], key)) {
      return length;
    }
  }
  return -1;
}

/**
 * The base implementation of `_.forEach` without support for iteratee shorthands.
 *
 * @private
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {Array|Object} Returns `collection`.
 */
//forEach基础实现
var baseEach = createBaseEach(baseForOwn);

/**
 * The base implementation of `baseForOwn` which iterates over `object`
 * properties returned by `keysFunc` and invokes `iteratee` for each property.
 * Iteratee functions may exit iteration early by explicitly returning `false`.
 *
 * @private
 * @param {Object} object The object to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @param {Function} keysFunc The function to get the keys of `object`.
 * @returns {Object} Returns `object`.
 */
//创建循环对象自身属性的基础方法
var baseFor = createBaseFor();

/**
 * The base implementation of `_.forOwn` without support for iteratee shorthands.
 *
 * @private
 * @param {Object} object The object to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {Object} Returns `object`.
 */
//forOwn的基础实现，循环对象自身属性
function baseForOwn(object, iteratee) {
  return object && baseFor(object, iteratee, keys);//调用baseFor处理
}

/**
 * The base implementation of `_.get` without support for default values.
 *
 * @private
 * @param {Object} object The object to query.
 * @param {Array|string} path The path of the property to get.
 * @returns {*} Returns the resolved value.
 */
//_.get方法的基础实现，获取object上path路径对应的值
function baseGet(object, path) {
  path = isKey(path, object) ? [path] : castPath(path);
  //判断path是不是合法key，如果是，就变成[path]，否则用castPath处理

  var index = 0,//循环路径数组的索引
      length = path.length;//路径数组的长度

  while (object != null && index < length) {//如果object不为空，循环路径数组
    object = object[toKey(path[index++])];//根据当前路径获取到深一层的对象或值赋值给object
  }
  return (index && index == length) ? object : undefined;
  //循环结束后返回找到的值，找不到返回undefined
}

/**
 * The base implementation of `_.invoke` without support for individual
 * method arguments.
 *
 * @private
 * @param {Object} object The object to query.
 * @param {Array|string} path The path of the method to invoke.
 * @param {Array} args The arguments to invoke the method with.
 * @returns {*} Returns the result of the invoked method.
 */
//_.invoke的基础实现。通过path路径查找到对象上对应的function，然后在路径数组倒数第二个路径对应对象上调用这个方法
function baseInvoke(object, path, args) {
  if (!isKey(path, object)) {//如果path不是合法object的key，说明是路径字符串
    path = castPath(path);//将path转换成路径数组
    object = parent(object, path);
    path = last(path);//最后一个路径，也就是要调用的方法对应的路径名
  }
  var func = object == null ? object : object[toKey(path)];
  return func == null ? undefined : apply(func, object, args);
}

/**
 * The base implementation of `_.isNative` without bad shim checks.
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a native function,
 *  else `false`.
 */
function baseIsNative(value) {
  if (!isObject(value) || isMasked(value)) {
    return false;
  }
  var pattern = (isFunction(value) || isHostObject(value)) ? reIsNative : reIsHostCtor;
  return pattern.test(toSource(value));
}

/**
 * The base implementation of `_.keys` which doesn't treat sparse arrays as dense.
 *
 * @private
 * @param {Object} object The object to query.
 * @returns {Array} Returns the array of property names.
 */
//_.keys的基础实现，类似于Object.keys()
function baseKeys(object) {
  if (!isPrototype(object)) {//如果object不是一个prototype对象，用nativekeys处理，也就是原生的Object.keys
    return nativeKeys(object);
  }
  var result = [];//结果数组
  for (var key in Object(object)) {//遍历object的属性
    if (hasOwnProperty.call(object, key) && key != 'constructor') {
      //如果当前key是object自身属性，并且不是构造函数，就插入结果数组
      result.push(key);
    }
  }
  return result;
}

/**
 * The base implementation of `_.rest` which doesn't validate or coerce arguments.
 *
 * @private
 * @param {Function} func The function to apply a rest parameter to.
 * @param {number} [start=func.length-1] The start position of the rest parameter.
 * @returns {Function} Returns the new function.
 */
//_.rest方法的基础实现，为函数实现ES6的rest参数
//rest参数的起始位置，默认是形参个数减去1，func.length - 1
function baseRest(func, start) {
  start = nativeMax(start === undefined ? (func.length - 1) : start, 0);
  //处理rest参数的起始位置,如果没传递start，就用函数形参个数减一，如果传递了，就在start和0之间选一个最大值
  return function() {
    var args = arguments,//函数接收到的参数数组
        index = -1,//循环索引
        length = nativeMax(args.length - start, 0),//rest参数的长度
        array = Array(length);//创建一个长度为rest参数长度的数组

    while (++index < length) {//循环rest参数长度，将rest参数全部存入array变量中
      array[index] = args[start + index];
    }
    index = -1;//循环参数
    var otherArgs = Array(start + 1);//创建一个数组存放除了rest参数以外的其他参数
    while (++index < start) {//循环获取其他参数存入otherArgs中
      otherArgs[index] = args[index];
    }
    otherArgs[start] = array;//otherArgs的最后一个参数就是rest参数数组
    return apply(func, this, otherArgs);//调用func，参数已处理成带有rest参数的形式
  };
}

/**
 * The base implementation of `_.slice` without an iteratee call guard.
 *
 * @private
 * @param {Array} array The array to slice.
 * @param {number} [start=0] The start position.
 * @param {number} [end=array.length] The end position.
 * @returns {Array} Returns the slice of `array`.
 */
//_.slice方法基础实现
//创建一个数组array的切片，从起始索引到结束索引，不包括结束索引
function baseSlice(array, start, end) {
  var index = -1,//循环索引
      length = array.length;//数组长度

  if (start < 0) {//起始索引是负数处理，是负数就相当于从末尾往开头数，也就是和lengh相加
    start = -start > length ? 0 : (length + start);//和length相加后如果还是小于0就等于0
  }
  end = end > length ? length : end;//结束索引如果大于length就让它等于length
  if (end < 0) {//处理结束索引是负数
    end += length;
  }
  length = start > end ? 0 : ((end - start) >>> 0);
  //根据start和end计算这个切片的长度，如果起始在结束后面那么切片长度为0，否则相减并且取整
  start >>>= 0;//start取整

  var result = Array(length);//结果切片数组
  while (++index < length) {//循环切片长度的次数，给结果数组每一项赋值
    result[index] = array[index + start];
  }
  return result;
}

/**
 * The base implementation of `_.toString` which doesn't convert nullish
 * values to empty strings.
 *
 * @private
 * @param {*} value The value to process.
 * @returns {string} Returns the string.
 */
//toString方法的基础实现
function baseToString(value) {
  // Exit early for strings to avoid a performance hit in some environments.
  if (typeof value == 'string') {//如果value已经是字符串，直接返回
    return value;
  }
  if (isSymbol(value)) {//如果value是symbol对象，就调用symbol原型上的toString方法转换成字符串
    return symbolToString ? symbolToString.call(value) : '';
  }
  var result = (value + '');//转换成字符串
  return (result == '0' && (1 / value) == -INFINITY) ? '-0' : result;//处理-0情况后返回结果字符串
}

/**
 * Casts `value` to a path array if it's not one.
 *
 * @private
 * @param {*} value The value to inspect.
 * @returns {Array} Returns the cast property path array.
 */
//将值计算成一个路径数组
function castPath(value) {
  return isArray(value) ? value : stringToPath(value);
}

/**
 * Creates a `baseEach` or `baseEachRight` function.
 *
 * @private
 * @param {Function} eachFunc The function to iterate over a collection.
 * @param {boolean} [fromRight] Specify iterating from right to left.
 * @returns {Function} Returns the new base function.
 */
//创建一个baseEach或者baseEachRight方法
function createBaseEach(eachFunc, fromRight) {
  return function(collection, iteratee) {
    if (collection == null) {//如果collection是空，直接返回
      return collection;
    }
    if (!isArrayLike(collection)) {//如果collection不是array-like对象，就用eachFunc
      return eachFunc(collection, iteratee);
    }
    var length = collection.length,//collection长度
        index = fromRight ? length : -1,//循环索引，如果fromRight就从结尾开始，否则从开头开始
        iterable = Object(collection);

    while ((fromRight ? index-- : ++index < length)) {//循环，如果iteratee返回false，跳出循环
      if (iteratee(iterable[index], index, iterable) === false) {
        break;
      }
    }
    return collection;
  };
}

/**
 * Creates a base function for methods like `_.forIn` and `_.forOwn`.
 *
 * @private
 * @param {boolean} [fromRight] Specify iterating from right to left.
 * @returns {Function} Returns the new base function.
 */
//类似forIn或者forOwn方法，用于循环对象的属性
function createBaseFor(fromRight) {
  return function(object, iteratee, keysFunc) {
    var index = -1,//循环索引
        iterable = Object(object),
        props = keysFunc(object),//对象的键组成的数组
        length = props.length;//键数组的长度

    while (length--) {//循环键数组
      var key = props[fromRight ? length : ++index];
      if (iteratee(iterable[key], key, iterable) === false) {
        //如果iteratee调用后返回false，就跳出循环
        break;
      }
    }
    return object;
  };
}

/**
 * Gets the data for `map`.
 *
 * @private
 * @param {Object} map The map to query.
 * @param {string} key The reference key.
 * @returns {*} Returns the map data.
 */
function getMapData(map, key) {
  var data = map.__data__;
  return isKeyable(key)
    ? data[typeof key == 'string' ? 'string' : 'hash']
    : data.map;
}

/**
 * Gets the native function at `key` of `object`.
 *
 * @private
 * @param {Object} object The object to query.
 * @param {string} key The key of the method to get.
 * @returns {*} Returns the function if it's native, else `undefined`.
 */
function getNative(object, key) {
  var value = getValue(object, key);
  return baseIsNative(value) ? value : undefined;
}

/**
 * Checks if `value` is a valid array-like index.
 *
 * @private
 * @param {*} value The value to check.
 * @param {number} [length=MAX_SAFE_INTEGER] The upper bounds of a valid index.
 * @returns {boolean} Returns `true` if `value` is a valid index, else `false`.
 */
//判断一个值是否是一个有效的array-like对象的索引
function isIndex(value, length) {
  length = length == null ? MAX_SAFE_INTEGER : length;
  return !!length &&
    (typeof value == 'number' || reIsUint.test(value)) &&
    (value > -1 && value % 1 == 0 && value < length);
}

/**
 * Checks if `value` is a property name and not a property path.
 *
 * @private
 * @param {*} value The value to check.
 * @param {Object} [object] The object to query keys on.
 * @returns {boolean} Returns `true` if `value` is a property name, else `false`.
 */
//检查一个值是一个合法属性名而不是属性路径
//value需要判断的值，object需要查询键的对象
function isKey(value, object) {
  if (isArray(value)) {//如果value是数组，返回false
    return false;
  }
  var type = typeof value;//value的typeof值
  if (type == 'number' || type == 'symbol' || type == 'boolean' ||
      value == null || isSymbol(value)) {
        //如果value是number、sumbol、boolean、null，说明是合法key，返回true
    return true;
  }
  return reIsPlainProp.test(value) || !reIsDeepProp.test(value) ||
    (object != null && value in Object(object));
    //reIsPlainProp = /^\w*$/   匹配单词，说明是属性名
    //reIsDeepProp = /\.|\[(?:[^[\]]*|(["'])(?:(?!\1)[^\\]|\\.)*?\1)\]/ 如果含有点.或者含有数组说明不是属性名
    //如果value在object里能找到说明是属性名
}

/**
 * Checks if `value` is suitable for use as unique object key.
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is suitable, else `false`.
 */
function isKeyable(value) {
  var type = typeof value;
  return (type == 'string' || type == 'number' || type == 'symbol' || type == 'boolean')
    ? (value !== '__proto__')
    : (value === null);
}

/**
 * Checks if `func` has its source masked.
 *
 * @private
 * @param {Function} func The function to check.
 * @returns {boolean} Returns `true` if `func` is masked, else `false`.
 */
function isMasked(func) {
  return !!maskSrcKey && (maskSrcKey in func);
}

/**
 * Checks if `value` is likely a prototype object.
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a prototype, else `false`.
 */
//判断一个值是否类似一个prototype对象
function isPrototype(value) {
  var Ctor = value && value.constructor,
      proto = (typeof Ctor == 'function' && Ctor.prototype) || objectProto;

  return value === proto;
}

/**
 * Gets the parent value at `path` of `object`.
 *
 * @private
 * @param {Object} object The object to query.
 * @param {Array} path The path to get the parent value of.
 * @returns {*} Returns the parent value.
 */
//根据对象的路径数组获取到倒数第二个父级值
function parent(object, path) {
  return path.length == 1 ? object : baseGet(object, baseSlice(path, 0, -1));
  //如果路径数组长度只有1，则父级就是object,否则调用baseGet获取到对应元素，用baseSlice截掉路径数组的最后一项
}

/**
 * Converts `string` to a property path array.
 *
 * @private
 * @param {string} string The string to convert.
 * @returns {Array} Returns the property path array.
 */
//将路径字符串转换成路径数组
var stringToPath = memoize(function(string) {
  string = toString(string);//将string转换成字符串格式

  var result = [];//结果数组
  if (reLeadingDot.test(string)) {
    //reLeadingDot = /^\./
    //如果字符串的开头如果是一个点，结果数组第一个路径值就push一个空字符串
    result.push('');
  }
  //rePropName = /[^.[\]]+|\[(?:(-?\d+(?:\.\d+)?)|(["'])((?:(?!\2)[^\\]|\\.)*?)\2)\]|(?=(?:\.|\[\])(?:\.|\[\]|$))/g
  string.replace(rePropName, function(match, number, quote, string) {
    result.push(quote ? string.replace(reEscapeChar, '$1') : (number || match));
    //如果捕获到了quote，处理转义字符后赋值给key然后push进结果
    //否则插入捕获到的number
  });
  return result;
});

/**
 * Converts `value` to a string key if it's not a string or symbol.
 *
 * @private
 * @param {*} value The value to inspect.
 * @returns {string|symbol} Returns the key.
 */
//将一个值转换成字符串键，如果它不是字符串或者symbol对象
function toKey(value) {
  if (typeof value == 'string' || isSymbol(value)) {//如果value已经是字符串或者symbol，直接返回
    return value;
  }
  var result = (value + '');//转成字符串
  return (result == '0' && (1 / value) == -INFINITY) ? '-0' : result;//处理-0的情况
}

/**
 * Converts `func` to its source code.
 *
 * @private
 * @param {Function} func The function to process.
 * @returns {string} Returns the source code.
 */
function toSource(func) {
  if (func != null) {
    try {
      return funcToString.call(func);
    } catch (e) {}
    try {
      return (func + '');
    } catch (e) {}
  }
  return '';
}

/**
 * Gets the last element of `array`.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Array
 * @param {Array} array The array to query.
 * @returns {*} Returns the last element of `array`.
 * @example
 *
 * _.last([1, 2, 3]);
 * // => 3
 */
//获取到数组最后一个元素
function last(array) {
  var length = array ? array.length : 0;//数组长度
  return length ? array[length - 1] : undefined;//返回最后一个元素，没有长度就返回undefined
}

/**
 * Invokes the method at `path` of each element in `collection`, returning
 * an array of the results of each invoked method. Any additional arguments
 * are provided to each invoked method. If `path` is a function, it's invoked
 * for, and `this` bound to, each element in `collection`.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Collection
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Array|Function|string} path The path of the method to invoke or
 *  the function invoked per iteration.
 * @param {...*} [args] The arguments to invoke each method with.
 * @returns {Array} Returns the array of results.
 * @example
 *
 * _.invokeMap([[5, 1, 7], [3, 2, 1]], 'sort');
 * // => [[1, 5, 7], [1, 2, 3]]
 *
 * _.invokeMap([123, 456], String.prototype.split, '');
 * // => [['1', '2', '3'], ['4', '5', '6']]
 */
//引用path参数对应的方法处理collection中的每一个元素，将引用方法处理后的结果组成一个数组返回。
//任何额外的参数都被传递给每一次引用方法的调用
//如果path参数是一个方法，直接调用，如果不是，就是路径数组或者路径字符串，就去那个路径下寻找对应的方法
//调用引用方法的时候this被绑定到collection的每一个元素上
var invokeMap = baseRest(function(collection, path, args) {
  var index = -1,//循环索引
      isFunc = typeof path == 'function',//path是否本身就是function
      isProp = isKey(path),//path是否本身就是对象的合法key
      result = isArrayLike(collection) ? Array(collection.length) : [];//结果数组

  baseEach(collection, function(value) {//调用baseEach循环collection
    var func = isFunc ? path : ((isProp && value != null) ? value[path] : undefined);
    //如果path本身就是function，直接用；如果path本身就是合法key，就取value[path]，否则func是undefined
    result[++index] = func ? apply(func, value, args) : baseInvoke(value, path, args);
    //结果数组的每个元素是调用func的返回值，如果有func直接apply调用，否则调用baseInvoke去通过路径查找到方法
  });
  return result;
});

/**
 * Creates a function that memoizes the result of `func`. If `resolver` is
 * provided, it determines the cache key for storing the result based on the
 * arguments provided to the memoized function. By default, the first argument
 * provided to the memoized function is used as the map cache key. The `func`
 * is invoked with the `this` binding of the memoized function.
 *
 * **Note:** The cache is exposed as the `cache` property on the memoized
 * function. Its creation may be customized by replacing the `_.memoize.Cache`
 * constructor with one whose instances implement the
 * [`Map`](http://ecma-international.org/ecma-262/7.0/#sec-properties-of-the-map-prototype-object)
 * method interface of `delete`, `get`, `has`, and `set`.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Function
 * @param {Function} func The function to have its output memoized.
 * @param {Function} [resolver] The function to resolve the cache key.
 * @returns {Function} Returns the new memoized function.
 * @example
 *
 * var object = { 'a': 1, 'b': 2 };
 * var other = { 'c': 3, 'd': 4 };
 *
 * var values = _.memoize(_.values);
 * values(object);
 * // => [1, 2]
 *
 * values(other);
 * // => [3, 4]
 *
 * object.a = 2;
 * values(object);
 * // => [1, 2]
 *
 * // Modify the result cache.
 * values.cache.set(object, ['a', 'b']);
 * values(object);
 * // => ['a', 'b']
 *
 * // Replace `_.memoize.Cache`.
 * _.memoize.Cache = WeakMap;
 */
//创建一个函数可以缓存func方法的结果。如果提供了resolver参数，它被用来计算缓存对象上的key，基于传递给已经memoize化的函数的参数。
//将计算结果缓存在闭包中的私有变量中，如果再次计算同样的值就直接获取
function memoize(func, resolver) {
  if (typeof func != 'function' || (resolver && typeof resolver != 'function')) {
    //func和resolver（如果提供的话）如果不是函数，抛错误
    throw new TypeError(FUNC_ERROR_TEXT);
  }
  var memoized = function() {
    var args = arguments,
        key = resolver ? resolver.apply(this, args) : args[0],
        //如果提供了resolver，就用resolver来确定key，否则key就是memoized的第一个参数
        cache = memoized.cache;//cashe对象

    if (cache.has(key)) {//如果cache中已经有此key，就直接获取后返回
      return cache.get(key);
    }
    var result = func.apply(this, args);//否则调用func计算出key对应的value
    memoized.cache = cache.set(key, result);//将新value存入cache后返回
    return result;
  };
  memoized.cache = new (memoize.Cache || MapCache);
  //cache对象被定义到memoized方法上，cache使用自定义的MapCache类型
  return memoized;//返回被memoize化的方法
}

// Assign cache to `_.memoize`.
memoize.Cache = MapCache;

/**
 * Performs a
 * [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
 * comparison between two values to determine if they are equivalent.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to compare.
 * @param {*} other The other value to compare.
 * @returns {boolean} Returns `true` if the values are equivalent, else `false`.
 * @example
 *
 * var object = { 'a': 1 };
 * var other = { 'a': 1 };
 *
 * _.eq(object, object);
 * // => true
 *
 * _.eq(object, other);
 * // => false
 *
 * _.eq('a', 'a');
 * // => true
 *
 * _.eq('a', Object('a'));
 * // => false
 *
 * _.eq(NaN, NaN);
 * // => true
 */
//使用SameValueZero规则判断两个值是否相等
function eq(value, other) {
  return value === other || (value !== value && other !== other);
}

/**
 * Checks if `value` is likely an `arguments` object.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an `arguments` object,
 *  else `false`.
 * @example
 *
 * _.isArguments(function() { return arguments; }());
 * // => true
 *
 * _.isArguments([1, 2, 3]);
 * // => false
 */
//判断一个值是一个类似arguments对象
function isArguments(value) {
  // Safari 8.1 makes `arguments.callee` enumerable in strict mode.
  return isArrayLikeObject(value) && hasOwnProperty.call(value, 'callee') &&
    (!propertyIsEnumerable.call(value, 'callee') || objectToString.call(value) == argsTag);
    //value是一个array-like对象，value有名为callee的自身属性，callee属性不可枚举，对象的toString标签是'[object Arguments]'
}

/**
 * Checks if `value` is classified as an `Array` object.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an array, else `false`.
 * @example
 *
 * _.isArray([1, 2, 3]);
 * // => true
 *
 * _.isArray(document.body.children);
 * // => false
 *
 * _.isArray('abc');
 * // => false
 *
 * _.isArray(_.noop);
 * // => false
 */
//判断一个值是否是数组
var isArray = Array.isArray;

/**
 * Checks if `value` is array-like. A value is considered array-like if it's
 * not a function and has a `value.length` that's an integer greater than or
 * equal to `0` and less than or equal to `Number.MAX_SAFE_INTEGER`.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is array-like, else `false`.
 * @example
 *
 * _.isArrayLike([1, 2, 3]);
 * // => true
 *
 * _.isArrayLike(document.body.children);
 * // => true
 *
 * _.isArrayLike('abc');
 * // => true
 *
 * _.isArrayLike(_.noop);
 * // => false
 */
//判断一个值是否是array-like对象
function isArrayLike(value) {
  return value != null && isLength(value.length) && !isFunction(value);
}

/**
 * This method is like `_.isArrayLike` except that it also checks if `value`
 * is an object.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an array-like object,
 *  else `false`.
 * @example
 *
 * _.isArrayLikeObject([1, 2, 3]);
 * // => true
 *
 * _.isArrayLikeObject(document.body.children);
 * // => true
 *
 * _.isArrayLikeObject('abc');
 * // => false
 *
 * _.isArrayLikeObject(_.noop);
 * // => false
 */
//判断一个值是不是一个array-like对象
//isObjectLike判断一个值是否是一个object-like，规则是：typeof返回object，并且不是null
//isArrayLike判断一个值是否是一个array-like，规则：不等于null，不是function类型，并且有length属性，length是大于0小于Number.MAX_SAFE_INTEGER的整数
function isArrayLikeObject(value) {
  return isObjectLike(value) && isArrayLike(value);
}

/**
 * Checks if `value` is classified as a `Function` object.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a function, else `false`.
 * @example
 *
 * _.isFunction(_);
 * // => true
 *
 * _.isFunction(/abc/);
 * // => false
 */
//判断一个值是否是function对象
function isFunction(value) {
  // The use of `Object#toString` avoids issues with the `typeof` operator
  // in Safari 8-9 which returns 'object' for typed array and other constructors.
  var tag = isObject(value) ? objectToString.call(value) : '';
  return tag == funcTag || tag == genTag;
}

/**
 * Checks if `value` is a valid array-like length.
 *
 * **Note:** This method is loosely based on
 * [`ToLength`](http://ecma-international.org/ecma-262/7.0/#sec-tolength).
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a valid length, else `false`.
 * @example
 *
 * _.isLength(3);
 * // => true
 *
 * _.isLength(Number.MIN_VALUE);
 * // => false
 *
 * _.isLength(Infinity);
 * // => false
 *
 * _.isLength('3');
 * // => false
 */
//判断一个值是否是一个有效的array-like对象的length属性
function isLength(value) {
  return typeof value == 'number' &&
    value > -1 && value % 1 == 0 && value <= MAX_SAFE_INTEGER;
}

/**
 * Checks if `value` is the
 * [language type](http://www.ecma-international.org/ecma-262/7.0/#sec-ecmascript-language-types)
 * of `Object`. (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an object, else `false`.
 * @example
 *
 * _.isObject({});
 * // => true
 *
 * _.isObject([1, 2, 3]);
 * // => true
 *
 * _.isObject(_.noop);
 * // => true
 *
 * _.isObject(null);
 * // => false
 */
//判断一个值是否是一个语言层面的对象
function isObject(value) {
  var type = typeof value;
  return !!value && (type == 'object' || type == 'function');
}

/**
 * Checks if `value` is object-like. A value is object-like if it's not `null`
 * and has a `typeof` result of "object".
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is object-like, else `false`.
 * @example
 *
 * _.isObjectLike({});
 * // => true
 *
 * _.isObjectLike([1, 2, 3]);
 * // => true
 *
 * _.isObjectLike(_.noop);
 * // => false
 *
 * _.isObjectLike(null);
 * // => false
 */
//判断一个值是否是一个object-like对象
function isObjectLike(value) {
  return !!value && typeof value == 'object';
}

/**
 * Checks if `value` is classified as a `Symbol` primitive or object.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a symbol, else `false`.
 * @example
 *
 * _.isSymbol(Symbol.iterator);
 * // => true
 *
 * _.isSymbol('abc');
 * // => false
 */
//判断一个值是否是一个symbol对象
function isSymbol(value) {
  return typeof value == 'symbol' ||
    (isObjectLike(value) && objectToString.call(value) == symbolTag);
}

/**
 * Converts `value` to a string. An empty string is returned for `null`
 * and `undefined` values. The sign of `-0` is preserved.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Lang
 * @param {*} value The value to process.
 * @returns {string} Returns the string.
 * @example
 *
 * _.toString(null);
 * // => ''
 *
 * _.toString(-0);
 * // => '-0'
 *
 * _.toString([1, 2, 3]);
 * // => '1,2,3'
 */
//将值转换为字符串，如果value是null或者undefined，返回空字符串。-0的符号会被保留
function toString(value) {
  return value == null ? '' : baseToString(value);
}

/**
 * Creates an array of the own enumerable property names of `object`.
 *
 * **Note:** Non-object values are coerced to objects. See the
 * [ES spec](http://ecma-international.org/ecma-262/7.0/#sec-object.keys)
 * for more details.
 *
 * @static
 * @since 0.1.0
 * @memberOf _
 * @category Object
 * @param {Object} object The object to query.
 * @returns {Array} Returns the array of property names.
 * @example
 *
 * function Foo() {
 *   this.a = 1;
 *   this.b = 2;
 * }
 *
 * Foo.prototype.c = 3;
 *
 * _.keys(new Foo);
 * // => ['a', 'b'] (iteration order is not guaranteed)
 *
 * _.keys('hi');
 * // => ['0', '1']
 */
//创建一个对象的自身可枚举属性名组成的数组，类似原生的Object.keys()
function keys(object) {
  return isArrayLike(object) ? arrayLikeKeys(object) : baseKeys(object);
  //如果object是array-like对象，调用arrayLikeKeys处理，否则使用baseKeys处理
}

module.exports = invokeMap;