underscore源码解析（实用的功能）

// Run Underscore.js in *noConflict* mode, returning the `_` variable to its
// previous owner. Returns a reference to the Underscore object.
//让渡_变量的控制权，以防冲突
_.noConflict = function() {
    root._ = previousUnderscore;
    return this;
};
// Keep the identity function around for default iteratees.
//默认的迭代器，直接返回参数
_.identity = function(value) {
    return value;
};

// Predicate-generating functions. Often useful outside of Underscore.
//不知道在哪里用的。。。。
_.constant = function(value) {
    return function() {
        return value;
    };
};

_.noop = function(){};
//返回键的值
_.property = function(key) {
    return function(obj) {
        return obj == null ? void 0 : obj[key];
    };
};

// Generates a function for a given object that returns a given property.
//和上面那个反一下
_.propertyOf = function(obj) {
    return obj == null ? function(){} : function(key) {
        return obj[key];
    };
};

// Returns a predicate for checking whether an object has a given set of
// `key:value` pairs.
//obj对象和json的匹配
_.matcher = _.matches = function(attrs) {
    attrs = _.extendOwn({}, attrs);
    return function(obj) {
        return _.isMatch(obj, attrs);
    };
};

// Run a function **n** times.
//执行N次函数
_.times = function(n, iteratee, context) {
    var accum = Array(Math.max(0, n));
    iteratee = optimizeCb(iteratee, context, 1);
    for (var i = 0; i < n; i++) accum[i] = iteratee(i);
    return accum;
};

// Return a random integer between min and max (inclusive).
//随机数
_.random = function(min, max) {
    if (max == null) {
        max = min;
        min = 0;
    }
    return min + Math.floor(Math.random() * (max - min + 1));
};

// A (possibly faster) way to get the current timestamp as an integer.
//当前时间撮
_.now = Date.now || function() {
        return new Date().getTime();
    };

// List of HTML entities for escaping.
var escapeMap = {
    '&': '&amp;',
    '<': '&lt;',
    '>': '&gt;',
    '"': '&quot;',
    "'": '&#x27;',
    '`': '&#x60;'
};
//对象的键值互换位置
var unescapeMap = _.invert(escapeMap);

// Functions for escaping and unescaping strings to/from HTML interpolation.
//html转换器
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;
    };
};



// 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;
};

// Generate a unique integer id (unique within the entire client session).
// Useful for temporary DOM ids.
//唯一的临时ID
var idCounter = 0;
_.uniqueId = function(prefix) {
    var id = ++idCounter + '';
    return prefix ? prefix + id : id;
};

哈哈哈哈哈，写的差不多了，其实underscore已经是早就过时的东西了，不过看看也有帮助（主要是其他太难，看不懂，哈哈哈哈哈）