// Object Functions
// ----------------
// Keys in IE < 9 that won't be iterated by `for key in ...` and thus missed.
var hasEnumBug = !{toString: null}.propertyIsEnumerable('toString');
var nonEnumerableProps = ['valueOf', 'isPrototypeOf', 'toString',
'propertyIsEnumerable', 'hasOwnProperty', 'toLocaleString'];
function collectNonEnumProps(obj, keys) {
var nonEnumIdx = nonEnumerableProps.length;
var constructor = obj.constructor;
var proto = (_.isFunction(constructor) && constructor.prototype) || ObjProto;
// Constructor is a special case.
var prop = 'constructor';
// _.contains() 为key添加枚举属性
if (_.has(obj, prop) && !_.contains(keys, prop)) keys.push(prop);
while (nonEnumIdx--) {
prop = nonEnumerableProps[nonEnumIdx];
if (prop in obj && obj[prop] !== proto[prop] && !_.contains(keys, prop)) {
keys.push(prop);
}
}
}
/*——————————————————————————————————————————————————————————————————————————*/
/**
* keys
* 检索object拥有的所有可枚举属性的名称。
*/
//
// Retrieve the names of an object's own properties.
// Delegates to **ECMAScript 5**'s native `Object.keys`
_.keys = function(obj) {
// 验证是否是obj
if (!_.isObject(obj)) return [];
// 如果支持原生
if (nativeKeys) return nativeKeys(obj);
var keys = [];
// 枚举
for (var key in obj) if (_.has(obj, key)) keys.push(key);
// Ahem, IE < 9. 兼容ie9 以下。给obj添加枚举属性
if (hasEnumBug) collectNonEnumProps(obj, keys);
return keys;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* keys
* 检索object拥有的和继承的所有属性的名称。
*/
// Retrieve all the property names of an object.
_.allKeys = function(obj) {
if (!_.isObject(obj)) return [];
var keys = [];
for (var key in obj) keys.push(key);
// Ahem, IE < 9.
if (hasEnumBug) collectNonEnumProps(obj, keys);
return keys;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* values
* 返回object对象所有的属性值。
*/
// Retrieve the values of an object's properties.
_.values = function(obj) {
var keys = _.keys(obj);
var length = keys.length;
var values = Array(length);
for (var i = 0; i < length; i++) {
// 返回所有的属性值
values[i] = obj[keys[i]];
}
return values;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* mapObject
* 它类似于map，但是这用于对象。转换每个属性的值。
*/
// Returns the results of applying the iteratee to each element of the object
// In contrast to _.map it returns an object
_.mapObject = function(obj, iteratee, context) {
iteratee = cb(iteratee, context);
var keys = _.keys(obj),
length = keys.length,
results = {},
currentKey;
for (var index = 0; index < length; index++) {
currentKey = keys[index];
// 目标key的值，等于自定义函数返回的key的值
results[currentKey] = iteratee(obj[currentKey], currentKey, obj);
}
return results;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* pairs
* 将对象转换为有两个值，类似键值对的数组
*/
// Convert an object into a list of `[key, value]` pairs.
_.pairs = function(obj) {
var keys = _.keys(obj);
var length = keys.length;
var pairs = Array(length);
for (var i = 0; i < length; i++) {
// 将key作为第一个值，value作为第二个值
pairs[i] = [keys[i], obj[keys[i]]];
}
return pairs;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* invert
* 返回一个object副本，使其键（keys）和值（values）对换。
*/
// Invert the keys and values of an object. The values must be serializable.
_.invert = function(obj) {
var result = {};
var keys = _.keys(obj);
for (var i = 0, length = keys.length; i < length; i++) {
result[obj[keys[i]]] = keys[i];
}
return result;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* functions
* 返回一个对象中的所有方法名，只返回function
*/
// Return a sorted list of the function names available on the object.
// Aliased as `methods`
_.functions = _.methods = function(obj) {
var names = [];
for (var key in obj) {
if (_.isFunction(obj[key])) names.push(key);
}
return names.sort();
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* extend
* 合并对象，相同的属性会覆盖
*/
// Extend a given object with all the properties in passed-in object(s).
_.extend = createAssigner(_.allKeys);
/*——————————————————————————————————————————————————————————————————————————*/
/**
* extend
* 合并对象属性，只合并对象的属性，相同会覆盖，不包括继承
*/
// Assigns a given object with all the own properties in the passed-in object(s)
// (https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object/assign)
_.extendOwn = _.assign = createAssigner(_.keys);
/*——————————————————————————————————————————————————————————————————————————*/
/**
* findKey
* 查找对象中是否存在KEY，找不到return undefined
*/
// Returns the first key on an object that passes a predicate test
_.findKey = function(obj, predicate, context) {
predicate = cb(predicate, context);
var keys = _.keys(obj), key;
for (var i = 0, length = keys.length; i < length; i++) {
key = keys[i];
if (predicate(obj[key], key, obj)) return key;
}
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* pick
* 返回一个object副本，只过滤出keys(有效的键组成的数组)参数指定的属性值。
*/
// Return a copy of the object only containing the whitelisted properties.
_.pick = function(object, oiteratee, context) {
var result = {}, obj = object, iteratee, keys;
if (obj == null) return result;
if (_.isFunction(oiteratee)) {
keys = _.allKeys(obj);
// 如果传进来的是一个比较函数，则使用
iteratee = optimizeCb(oiteratee, context);
} else {
keys = flatten(arguments, false, false, 1);
// 如果不是，则判断他的key 是否在obj中
iteratee = function(value, key, obj) { return key in obj; };
obj = Object(obj);
}
for (var i = 0, length = keys.length; i < length; i++) {
var key = keys[i];
var value = obj[key];
if (iteratee(value, key, obj)) result[key] = value;
}
return result;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* omit
* 返回一个object副本，只过滤出除去keys(有效的键组成的数组)参数指定的属性值。 -> 算是反pick 找剩下的。
*/
// Return a copy of the object without the blacklisted properties.
_.omit = function(obj, iteratee, context) {
if (_.isFunction(iteratee)) {
// negate 返回自定义函数的一个否定版本
iteratee = _.negate(iteratee);
} else {
var keys = _.map(flatten(arguments, false, false, 1), String);
iteratee = function(value, key) {
// 存在的全部取反
return !_.contains(keys, key);
};
}
// 然后再次调用pick
return _.pick(obj, iteratee, context);
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* defaults
* 填充默认参数
*/
// Fill in a given object with default properties.
_.defaults = createAssigner(_.allKeys, true);
/*——————————————————————————————————————————————————————————————————————————*/
/**
* defaults
* 创建具有给定原型的新对象， 可选附加props 作为 own的属性。 基本上，和Object.create一样， 但是没有所有的属性描述符。
*/
// Creates an object that inherits from the given prototype object.
// If additional properties are provided then they will be added to the
// created object.
_.create = function(prototype, props) {
// 创建一个原型对象
var result = baseCreate(prototype);
// 将目标属性全部添加到原型上
if (props) _.extendOwn(result, props);
return result;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* defaults
* 创建 一个浅复制（浅拷贝）的克隆object。任何嵌套的对象或数组都通过引用拷贝，不会复制。
*/
// Create a (shallow-cloned) duplicate of an object.
_.clone = function(obj) {
if (!_.isObject(obj)) return obj;
return _.isArray(obj) ? obj.slice() : _.extend({}, obj);
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* tap
* 用 object作为参数来调用函数interceptor，然后返回object。
*/
// Invokes interceptor with the obj, and then returns obj.
// The primary purpose of this method is to "tap into" a method chain, in
// order to perform operations on intermediate results within the chain.
_.tap = function(obj, interceptor) {
// 类似执行一个中间件函数，但是对结果不会产生任何影响
interceptor(obj);
return obj;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* isMatch
* Match：相同
* 告诉你properties中的键和值是否包含在object中。
*/
// Returns whether an object has a given set of `key:value` pairs.
_.isMatch = function(object, attrs) {
var keys = _.keys(attrs), length = keys.length;
if (object == null) return !length;
var obj = Object(object);
for (var i = 0; i < length; i++) {
var key = keys[i];
// 两个的键值对不相等，或者obj中没有这个key ，则返回false
if (attrs[key] !== obj[key] || !(key in obj)) return false;
}
return true;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* isEqual
* Match：相同
* 比较两个对象是否完全像等
*/
// Internal recursive comparison function for `isEqual`.
var eq = function(a, b, aStack, bStack) {
// Identical objects are equal. `0 === -0`, but they aren't identical.
// See the [Harmony `egal` proposal](http://wiki.ecmascript.org/doku.php?id=harmony:egal).
// 兼容 `0 === -0`，返回false
if (a === b) return a !== 0 || 1 / a === 1 / b;
// A strict comparison is necessary because `null == undefined`.
// 比较 null 和 undefined
if (a == null || b == null) return a === b;
// Unwrap any wrapped objects.
// 打开任何包裹物。
if (a instanceof _) a = a._wrapped;
if (b instanceof _) b = b._wrapped;
// Compare `[[Class]]` names.
// 如果名字不一样
var className = toString.call(a);
if (className !== toString.call(b)) return false;
switch (className) {
// 正则
// Strings, numbers, regular expressions, dates, and booleans are compared by value.
case '[object RegExp]':
// RegExps are coerced to strings for comparison (Note: '' + /a/i === '/a/i')
case '[object String]':
// Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
// equivalent to `new String("5")`.
// toString
return '' + a === '' + b;
case '[object Number]':
// `NaN`s are equivalent, but non-reflexive.
// 转数字
// Object(NaN) is equivalent to NaN
if (+a !== +a) return +b !== +b;
// An `egal` comparison is performed for other numeric values.
// 仍然兼容0
return +a === 0 ? 1 / +a === 1 / b : +a === +b;
case '[object Date]':
case '[object Boolean]':
// Coerce dates and booleans to numeric primitive values. Dates are compared by their
// millisecond representations. Note that invalid dates with millisecond representations
// of `NaN` are not equivalent.
// 转换为数字
return +a === +b;
}
// 比较数组
var areArrays = className === '[object Array]';
if (!areArrays) {
if (typeof a != 'object' || typeof b != 'object') return false;
// Objects with different constructors are not equivalent, but `Object`s or `Array`s
// from different frames are.
var aCtor = a.constructor, bCtor = b.constructor;
if (aCtor !== bCtor && !(_.isFunction(aCtor) && aCtor instanceof aCtor &&
_.isFunction(bCtor) && bCtor instanceof bCtor)
&& ('constructor' in a && 'constructor' in b)) {
return false;
}
}
// Assume equality for cyclic structures. The algorithm for detecting cyclic
// structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
// Initializing stack of traversed objects.
// It's done here since we only need them for objects and arrays comparison.
aStack = aStack || [];
bStack = bStack || [];
var length = aStack.length;
while (length--) {
// Linear search. Performance is inversely proportional to the number of
// unique nested structures.
if (aStack[length] === a) return bStack[length] === b;
}
// Add the first object to the stack of traversed objects.
aStack.push(a);
bStack.push(b);
// Recursively compare objects and arrays.
if (areArrays) {
// Compare array lengths to determine if a deep comparison is necessary.
length = a.length;
if (length !== b.length) return false;
// Deep compare the contents, ignoring non-numeric properties.
while (length--) {
if (!eq(a[length], b[length], aStack, bStack)) return false;
}
} else {
// Deep compare objects.
var keys = _.keys(a), key;
length = keys.length;
// Ensure that both objects contain the same number of properties before comparing deep equality.
if (_.keys(b).length !== length) return false;
while (length--) {
// Deep compare each member
key = keys[length];
if (!(_.has(b, key) && eq(a[key], b[key], aStack, bStack))) return false;
}
}
// Remove the first object from the stack of traversed objects.
aStack.pop();
bStack.pop();
return true;
};
// Perform a deep comparison to check if two objects are equal.
_.isEqual = function(a, b) {
return eq(a, b);
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* isEmpty
* 判断是否为空，没有可枚举属性也为true
*/
// Is a given array, string, or object empty?
// An "empty" object has no enumerable own-properties.
_.isEmpty = function(obj) {
if (obj == null) return true;
if (isArrayLike(obj) && (_.isArray(obj) || _.isString(obj) || _.isArguments(obj))) return obj.length === 0;
return _.keys(obj).length === 0;
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* isElement
* 判断是否为element
*/
// Is a given value a DOM element?
_.isElement = function(obj) {
return !!(obj && obj.nodeType === 1);
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* isArray
* 判断是否为Array
*/
// Is a given value an array?
// Delegates to ECMA5's native Array.isArray
_.isArray = nativeIsArray || function(obj) {
// 使用toString 方法比较
return toString.call(obj) === '[object Array]';
};
/*——————————————————————————————————————————————————————————————————————————*/
/**
* isObject
* func 和 obj 都是obj
*/
// Is a given variable an object?
_.isObject = function(obj) {
var type = typeof obj;
return type === 'function' || type === 'object' && !!obj;
};
// 为这些方法添加公共函数
// Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp, isError.
_.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp', 'Error'], function(name) {
_['is' + name] = function(obj) {
return toString.call(obj) === '[object ' + name + ']';
};
});
// Define a fallback version of the method in browsers (ahem, IE < 9), where
// there isn't any inspectable "Arguments" type.
// 如果_.isArguments() 返回了false ，然后在检查里面是否有callee属性，有则为arguments
if (!_.isArguments(arguments)) {
_.isArguments = function(obj) {
return _.has(obj, 'callee');
};
}
// 兼容旧V8 & ie11 & Safari 8
// Optimize `isFunction` if appropriate. Work around some typeof bugs in old v8,
// IE 11 (#1621), and in Safari 8 (#1929).
if (typeof /./ != 'function' && typeof Int8Array != 'object') {
_.isFunction = function(obj) {
return typeof obj == 'function' || false;
};
}
// 如果object是一个有限的数字，返回true。
// Is a given object a finite number?
_.isFinite = function(obj) {
return isFinite(obj) && !isNaN(parseFloat(obj));
};
// 判断是否为NaN
// Is the given value `NaN`? (NaN is the only number which does not equal itself).
_.isNaN = function(obj) {
return _.isNumber(obj) && obj !== +obj;
};
// 是否为布尔值
// Is a given value a boolean?
_.isBoolean = function(obj) {
return obj === true || obj === false || toString.call(obj) === '[object Boolean]';
};
// 是否是null
// Is a given value equal to null?
_.isNull = function(obj) {
return obj === null;
};
// 是否是undefined
// Is a given variable undefined?
_.isUndefined = function(obj) {
return obj === void 0;
};
// 对象是否包含给定的键吗？
// hasOwnProperty 是JavaScript中唯一一个处理属性但是不需要查找原型链的方法。
// Shortcut function for checking if an object has a given property directly
// on itself (in other words, not on a prototype).
_.has = function(obj, key) {
return obj != null && hasOwnProperty.call(obj, key);
};
// Utility Functions
// -----------------
// 放弃Underscore 的控制变量"_"。返回Underscore 对象的引用。
// Run Underscore.js in *noConflict* mode, returning the `_` variable to its
// previous owner. Returns a reference to the Underscore object.
_.noConflict = function() {
root._ = previousUnderscore;
return this;
};
// 返回与传入参数相等的值. 相当于数学里的: f(x) = x
// Keep the identity function around for default iteratees.
_.identity = function(value) {
return value;
};
// 创建一个函数，这个函数 返回相同的值 用来作为_.constant的参数。
// Predicate-generating functions. Often useful outside of Underscore.
_.constant = function(value) {
return function() {
return value;
};
};
// 返回undefined，不论传递给它的是什么参数。 可以用作默认可选的回调参数。
_.noop = function(){};
// 返回一个函数，这个函数返回任何传入的对象的key属性。
_.property = function(key) {
return function(obj) {
return obj == null ? void 0 : obj[key];
};
};
// 和_.property相反。需要一个对象，并返回一个函数,这个函数将返回一个提供的属性的值。
// Generates a function for a given object that returns a given property.
_.propertyOf = function(obj) {
return obj == null ? function(){} : function(key) {
return obj[key];
};
};
//返回一个断言函数，这个函数会给你一个断言可以用来辨别给定的对象是否匹配attrs指定键/值属性。
// Returns a predicate for checking whether an object has a given set of
// `key:value` pairs.
_.matcher = _.matches = function(attrs) {
attrs = _.extendOwn({}, attrs);
return function(obj) {
// attrs 是否存在于obj
return _.isMatch(obj, attrs);
};
};
//调用给定的迭代函数n次,
// Run a function **n** times.
_.times = function(n, iteratee, context) {
// 指定次数，否则为零
var accum = Array(Math.max(0, n));
iteratee = optimizeCb(iteratee, context, 1);
// 回调函数传入index，并将返回值保存起来，最后一次返回
for (var i = 0; i < n; i++) accum[i] = iteratee(i);
return accum;
};
// 返回一个min 和 max之间的随机整数。如果你只传递一个参数，那么将返回0和这个参数之间的整数。
// Return a random integer between min and max (inclusive).
_.random = function(min, max) {
if (max == null) {
max = min;
min = 0;
}
return min + Math.floor(Math.random() * (max - min + 1));
};
// 一个优化的方式来获得一个当前时间的整数时间戳。可用于实现定时/动画功能。
// A (possibly faster) way to get the current timestamp as an integer.
_.now = Date.now || function() {
return new Date().getTime();
};
// List of HTML entities for escaping.
var escapeMap = {
'&': '&',
'<': '<',
'>': '>',
'"': '"',
"'": ''',
'`': '`'
};
var unescapeMap = _.invert(escapeMap);
// Functions for escaping and unescaping strings to/from HTML interpolation.
var createEscaper = function(map) {
var escaper = function(match) {
return map[match];
};
// Regexes for identifying a key that needs to be escaped
var source = '(?:' + _.keys(map).join('|') + ')';
var testRegexp = RegExp(source);
var replaceRegexp = RegExp(source, 'g');
return function(string) {
string = string == null ? '' : '' + string;
return testRegexp.test(string) ? string.replace(replaceRegexp, escaper) : string;
};
};
// 转义HTML字符串，替换&, <, >, ", ', 和 /字符。
_.escape = createEscaper(escapeMap);
// 相反
_.unescape = createEscaper(unescapeMap);
// 如果指定的property 的值是一个函数，那么将在object上下文内调用它;否则，返回它。如果提供默认值，并且属性不存在，那么默认值将被返回。
// 如果设置defaultValue是一个函数，它的结果将被返回。
// If the value of the named `property` is a function then invoke it with the
// `object` as context; otherwise, return it.
_.result = function(object, property, fallback) {
var value = object == null ? void 0 : object[property];
if (value === void 0) {
value = fallback;
}
return _.isFunction(value) ? value.call(object) : value;
};
// 为需要的客户端模型或DOM元素生成一个全局唯一的id。如果prefix参数存在， id 将附加给它。
// Generate a unique integer id (unique within the entire client session).
// Useful for temporary DOM ids.
var idCounter = 0;
_.uniqueId = function(prefix) {
var id = ++idCounter + '';
return prefix ? prefix + id : id;
};
// By default, Underscore uses ERB-style template delimiters, change the
// following template settings to use alternative delimiters.
_.templateSettings = {
evaluate : /<%([\s\S]+?)%>/g,
interpolate : /<%=([\s\S]+?)%>/g,
escape : /<%-([\s\S]+?)%>/g
};
// When customizing `templateSettings`, if you don't want to define an
// interpolation, evaluation or escaping regex, we need one that is
// guaranteed not to match.
var noMatch = /(.)^/;
// Certain characters need to be escaped so that they can be put into a
// string literal.
var escapes = {
"'": "'",
'\\': '\\',
'\r': 'r',
'\n': 'n',
'\u2028': 'u2028',
'\u2029': 'u2029'
};
var escaper = /\\|'|\r|\n|\u2028|\u2029/g;
var escapeChar = function(match) {
return '\\' + escapes[match];
};
// JavaScript micro-templating, similar to John Resig's implementation.
// Underscore templating handles arbitrary delimiters, preserves whitespace,
// and correctly escapes quotes within interpolated code.
// NB: `oldSettings` only exists for backwards compatibility.
_.template = function(text, settings, oldSettings) {
if (!settings && oldSettings) settings = oldSettings;
settings = _.defaults({}, settings, _.templateSettings);
// Combine delimiters into one regular expression via alternation.
var matcher = RegExp([
(settings.escape || noMatch).source,
(settings.interpolate || noMatch).source,
(settings.evaluate || noMatch).source
].join('|') + '|$', 'g');
// Compile the template source, escaping string literals appropriately.
var index = 0;
var source = "__p+='";
text.replace(matcher, function(match, escape, interpolate, evaluate, offset) {
source += text.slice(index, offset).replace(escaper, escapeChar);
index = offset + match.length;
if (escape) {
source += "'+\n((__t=(" + escape + "))==null?'':_.escape(__t))+\n'";
} else if (interpolate) {
source += "'+\n((__t=(" + interpolate + "))==null?'':__t)+\n'";
} else if (evaluate) {
source += "';\n" + evaluate + "\n__p+='";
}
// Adobe VMs need the match returned to produce the correct offest.
return match;
});
source += "';\n";
// If a variable is not specified, place data values in local scope.
if (!settings.variable) source = 'with(obj||{}){\n' + source + '}\n';
source = "var __t,__p='',__j=Array.prototype.join," +
"print=function(){__p+=__j.call(arguments,'');};\n" +
source + 'return __p;\n';
try {
var render = new Function(settings.variable || 'obj', '_', source);
} catch (e) {
e.source = source;
throw e;
}
var template = function(data) {
return render.call(this, data, _);
};
// Provide the compiled source as a convenience for precompilation.
var argument = settings.variable || 'obj';
template.source = 'function(' + argument + '){\n' + source + '}';
return template;
};
// 返回一个封装的对象. 在封装的对象上调用方法会返回封装的对象本身, 直道 value 方法调用为止.
// Add a "chain" function. Start chaining a wrapped Underscore object.
_.chain = function(obj) {
var instance = _(obj);
instance._chain = true;
return instance;
};
// OOP
// ---------------
// If Underscore is called as a function, it returns a wrapped object that
// can be used OO-style. This wrapper holds altered versions of all the
// underscore functions. Wrapped objects may be chained.
// Helper function to continue chaining intermediate results.
var result = function(instance, obj) {
return instance._chain ? _(obj).chain() : obj;
};
// Add your own custom functions to the Underscore object.
_.mixin = function(obj) {
_.each(_.functions(obj), function(name) {
var func = _[name] = obj[name];
_.prototype[name] = function() {
var args = [this._wrapped];
push.apply(args, arguments);
return result(this, func.apply(_, args));
};
});
};
// Add all of the Underscore functions to the wrapper object.
_.mixin(_);
// 将原生的这几个方法也绑定在_ 上
// Add all mutator Array functions to the wrapper.
_.each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
var method = ArrayProto[name];
_.prototype[name] = function() {
var obj = this._wrapped;
method.apply(obj, arguments);
if ((name === 'shift' || name === 'splice') && obj.length === 0) delete obj[0];
return result(this, obj);
};
});
// 将原生的这几个方法也绑定在_ 上
// Add all accessor Array functions to the wrapper.
_.each(['concat', 'join', 'slice'], function(name) {
var method = ArrayProto[name];
_.prototype[name] = function() {
return result(this, method.apply(this._wrapped, arguments));
};
});
// Extracts the result from a wrapped and chained object.
_.prototype.value = function() {
return this._wrapped;
};
// Provide unwrapping proxy for some methods used in engine operations
// such as arithmetic and JSON stringification.
_.prototype.valueOf = _.prototype.toJSON = _.prototype.value;
_.prototype.toString = function() {
return '' + this._wrapped;
};