lib : underscore
version : v 1.5.0
reader : hooper
time : 2017-08-22 14:14:36
homepage : https://hcthink.github.io/h-blog/
code source : https://github.com/jashkenas/underscore/blob/v1.9.0/underscore.js
直接提供对应版本源码进行分析, 如有 demo. 专门贴出
// Underscore.js 1.5.0
// http://underscorejs.org
// (c) 2009-2011 Jeremy Ashkenas, DocumentCloud Inc.
// (c) 2011-2013 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
// Underscore may be freely distributed under the MIT license.
// 无传入方式的自调用块. 作用不多说, 避免污染全局.
// 1.5 的版本使用 .call(this) 的方式指定了 this.
// 对应的两个版本都没有. 实际上 un 在首行用 root 承接了 this. 不传入也不会有太大的作用域查询消耗.
(function() {
// Baseline setup
// --------------
// Establish the root object, `window` in the browser, or `global` on the server.
var root = this;
// Save the previous value of the `_` variable.
// 提供给 noConflict 作用参考: [underscore readme.md](./readme.md)
var previousUnderscore = root._;
// Establish the object that gets returned to break out of a loop iteration.
var breaker = {};
/*
有一长段的代码去获取 js api 操作的引用.
在支持的环境,可以用于校验传入的对象操作的合法性, 并利用该操作完成作业
if (nativeReduce && obj.reduce === nativeReduce) {
if (context) iterator = _.bind(iterator, context);
return initial ? obj.reduce(iterator, memo) : obj.reduce(iterator);
}
别忘了他的另一个作用: 可压缩性
*/
// Save bytes in the minified (but not gzipped) version:
var ArrayProto = Array.prototype,
ObjProto = Object.prototype,
FuncProto = Function.prototype;
// Create quick reference variables for speed access to core prototypes.
var push = ArrayProto.push,
slice = ArrayProto.slice,
concat = ArrayProto.concat,
toString = ObjProto.toString,
hasOwnProperty = ObjProto.hasOwnProperty;
// All **ECMAScript 5** native function implementations that we hope to use
// are declared here.
var nativeForEach = ArrayProto.forEach,
nativeMap = ArrayProto.map,
nativeReduce = ArrayProto.reduce,
nativeReduceRight = ArrayProto.reduceRight,
nativeFilter = ArrayProto.filter,
nativeEvery = ArrayProto.every,
nativeSome = ArrayProto.some,
nativeIndexOf = ArrayProto.indexOf,
nativeLastIndexOf = ArrayProto.lastIndexOf,
nativeIsArray = Array.isArray,
nativeKeys = Object.keys,
nativeBind = FuncProto.bind;
// Create a safe reference to the Underscore object for use below.
// 如果使用 _(obj) 的方式调用, 则需要做一些兼容处理,确保返回正确的 underscore 实例
var _ = function(obj) {
if (obj instanceof _)
return obj;
if (!(this instanceof _))
return new _(obj);
this._wrapped = obj;
};
// Export the Underscore object for **Node.js**, with
// backwards-compatibility for the old `require()` API. If we're in
// the browser, add `_` as a global object via a string identifier,
// for Closure Compiler "advanced" mode.
// 兼容 node 和浏览器两种. 之前有些版本并没有在 else 中处理 root._ = _;
// 这会导致宿主和 require 两种方式都能获取 _
if (typeof exports !== 'undefined') {
if (typeof module !== 'undefined' && module.exports) {
exports = module.exports = _;
}
exports._ = _;
} else {
root._ = _;
}
// Current version.
_.VERSION = '1.5.0';
// Collection Functions
// --------------------
// The cornerstone, an `each` implementation, aka `forEach`.
// Handles objects with the built-in `forEach`, arrays, and raw objects.
// Delegates to **ECMAScript 5**'s native `forEach` if available.
var each = _.each = _.forEach = function(obj, iterator, context) {
if (obj == null)
return;
if (nativeForEach && obj.forEach === nativeForEach) {
obj.forEach(iterator, context);
} else if (obj.length === + obj.length) {
for (var i = 0, l = obj.length; i < l; i++) {
if (iterator.call(context, obj[i], i, obj) === breaker)
return;
}
} else {
for (var key in obj) {
if (_.has(obj, key)) {
if (iterator.call(context, obj[key], key, obj) === breaker)
return;
}
}
}
};
// Return the results of applying the iterator to each element.
// Delegates to **ECMAScript 5**'s native `map` if available.
_.map = _.collect = function(obj, iterator, context) {
var results = [];
if (obj == null)
return results;
if (nativeMap && obj.map === nativeMap)
return obj.map(iterator, context);
each(obj, function(value, index, list) {
results.push(iterator.call(context, value, index, list));
});
return results;
};
var reduceError = 'Reduce of empty array with no initial value';
// **Reduce** builds up a single result from a list of values, aka `inject`,
// or `foldl`. Delegates to **ECMAScript 5**'s native `reduce` if available.
_.reduce = _.foldl = _.inject = function(obj, iterator, memo, context) {
var initial = arguments.length > 2;
if (obj == null)
obj = [];
if (nativeReduce && obj.reduce === nativeReduce) {
if (context)
iterator = _.bind(iterator, context);
return initial
? obj.reduce(iterator, memo)
: obj.reduce(iterator);
}
each(obj, function(value, index, list) {
if (!initial) {
memo = value;
initial = true;
} else {
memo = iterator.call(context, memo, value, index, list);
}
});
if (!initial)
throw new TypeError(reduceError);
return memo;
};
// The right-associative version of reduce, also known as `foldr`.
// Delegates to **ECMAScript 5**'s native `reduceRight` if available.
_.reduceRight = _.foldr = function(obj, iterator, memo, context) {
var initial = arguments.length > 2;
if (obj == null)
obj = [];
if (nativeReduceRight && obj.reduceRight === nativeReduceRight) {
if (context)
iterator = _.bind(iterator, context);
return initial
? obj.reduceRight(iterator, memo)
: obj.reduceRight(iterator);
}
var length = obj.length;
if (length !== + length) {
var keys = _.keys(obj);
length = keys.length;
}
each(obj, function(value, index, list) {
index = keys
? keys[--length]
: --length;
if (!initial) {
memo = obj[index];
initial = true;
} else {
memo = iterator.call(context, memo, obj[index], index, list);
}
});
if (!initial)
throw new TypeError(reduceError);
return memo;
};
// Return the first value which passes a truth test. Aliased as `detect`.
_.find = _.detect = function(obj, iterator, context) {
var result;
any(obj, function(value, index, list) {
if (iterator.call(context, value, index, list)) {
result = value;
return true;
}
});
return result;
};
// Return all the elements that pass a truth test.
// Delegates to **ECMAScript 5**'s native `filter` if available.
// Aliased as `select`.
_.filter = _.select = function(obj, iterator, context) {
var results = [];
if (obj == null)
return results;
if (nativeFilter && obj.filter === nativeFilter)
return obj.filter(iterator, context);
each(obj, function(value, index, list) {
if (iterator.call(context, value, index, list))
results.push(value);
}
);
return results;
};
// Return all the elements for which a truth test fails.
_.reject = function(obj, iterator, context) {
return _.filter(obj, function(value, index, list) {
return !iterator.call(context, value, index, list);
}, context);
};
// Determine whether all of the elements match a truth test.
// Delegates to **ECMAScript 5**'s native `every` if available.
// Aliased as `all`.
_.every = _.all = function(obj, iterator, context) {
iterator || (iterator = _.identity);
var result = true;
if (obj == null)
return result;
if (nativeEvery && obj.every === nativeEvery)
return obj.every(iterator, context);
each(obj, function(value, index, list) {
if (!(result = result && iterator.call(context, value, index, list)))
return breaker;
}
);
return !!result;
};
// Determine if at least one element in the object matches a truth test.
// Delegates to **ECMAScript 5**'s native `some` if available.
// Aliased as `any`.
var any = _.some = _.any = function(obj, iterator, context) {
iterator || (iterator = _.identity);
var result = false;
if (obj == null)
return result;
if (nativeSome && obj.some === nativeSome)
return obj.some(iterator, context);
each(obj, function(value, index, list) {
if (result || (result = iterator.call(context, value, index, list)))
return breaker;
}
);
return !!result;
};
// Determine if the array or object contains a given value (using `===`).
// Aliased as `include`.
_.contains = _.include = function(obj, target) {
if (obj == null)
return false;
if (nativeIndexOf && obj.indexOf === nativeIndexOf)
return obj.indexOf(target) != -1;
return any(obj, function(value) {
return value === target;
});
};
// Invoke a method (with arguments) on every item in a collection.
_.invoke = function(obj, method) {
var args = slice.call(arguments, 2);
var isFunc = _.isFunction(method);
return _.map(obj, function(value) {
return (isFunc
? method
: value[method]).apply(value, args);
});
};
// Convenience version of a common use case of `map`: fetching a property.
_.pluck = function(obj, key) {
return _.map(obj, function(value) {
return value[key];
});
};
// Convenience version of a common use case of `filter`: selecting only objects
// containing specific `key:value` pairs.
_.where = function(obj, attrs, first) {
if (_.isEmpty(attrs))
return first
? void 0
: [];
return _[first
? 'find'
: 'filter'](obj, function(value) {
for (var key in attrs) {
if (attrs[key] !== value[key])
return false;
}
return true;
});
};
// Convenience version of a common use case of `find`: getting the first object
// containing specific `key:value` pairs.
_.findWhere = function(obj, attrs) {
return _.where(obj, attrs, true);
};
// Return the maximum element or (element-based computation).
// Can't optimize arrays of integers longer than 65,535 elements.
// See [WebKit Bug 80797](https://bugs.webkit.org/show_bug.cgi?id=80797)
_.max = function(obj, iterator, context) {
if (!iterator && _.isArray(obj) && obj[0] === + obj[0] && obj.length < 65535) {
return Math.max.apply(Math, obj);
}
if (!iterator && _.isEmpty(obj))
return -Infinity;
var result = {
computed: -Infinity,
value: -Infinity
};
each(obj, function(value, index, list) {
var computed = iterator
? iterator.call(context, value, index, list)
: value;
computed > result.computed && (result = {
value: value,
computed: computed
});
});
return result.value;
};
// Return the minimum element (or element-based computation).
_.min = function(obj, iterator, context) {
if (!iterator && _.isArray(obj) && obj[0] === + obj[0] && obj.length < 65535) {
return Math.min.apply(Math, obj);
}
if (!iterator && _.isEmpty(obj))
return Infinity;
var result = {
computed: Infinity,
value: Infinity
};
each(obj, function(value, index, list) {
var computed = iterator
? iterator.call(context, value, index, list)
: value;
computed < result.computed && (result = {
value: value,
computed: computed
});
});
return result.value;
};
// Shuffle an array.
_.shuffle = function(obj) {
var rand;
var index = 0;
var shuffled = [];
each(obj, function(value) {
rand = _.random(index++);
shuffled[index - 1] = shuffled[rand];
shuffled[rand] = value;
});
return shuffled;
};
// An internal function to generate lookup iterators.
var lookupIterator = function(value) {
return _.isFunction(value)
? value
: function(obj) {
return obj[value];
};
};
// Sort the object's values by a criterion produced by an iterator.
_.sortBy = function(obj, value, context) {
var iterator = lookupIterator(value);
return _.pluck(_.map(obj, function(value, index, list) {
return {
value: value,
index: index,
criteria: iterator.call(context, value, index, list)
};
}).sort(function(left, right) {
var a = left.criteria;
var b = right.criteria;
if (a !== b) {
if (a > b || a === void 0)
return 1;
if (a < b || b === void 0)
return -1;
}
return left.index < right.index
? -1
: 1;
}), 'value');
};
// An internal function used for aggregate "group by" operations.
var group = function(obj, value, context, behavior) {
var result = {};
var iterator = lookupIterator(value == null
? _.identity
: value);
each(obj, function(value, index) {
var key = iterator.call(context, value, index, obj);
behavior(result, key, value);
});
return result;
};
// Groups the object's values by a criterion. Pass either a string attribute
// to group by, or a function that returns the criterion.
_.groupBy = function(obj, value, context) {
return group(obj, value, context, function(result, key, value) {
(_.has(result, key)
? result[key]
: (result[key] = [])).push(value);
});
};
// Counts instances of an object that group by a certain criterion. Pass
// either a string attribute to count by, or a function that returns the
// criterion.
_.countBy = function(obj, value, context) {
return group(obj, value, context, function(result, key) {
if (!_.has(result, key))
result[key] = 0;
result[key]++;
});
};
// Use a comparator function to figure out the smallest index at which
// an object should be inserted so as to maintain order. Uses binary search.
_.sortedIndex = function(array, obj, iterator, context) {
iterator = iterator == null
? _.identity
: lookupIterator(iterator);
var value = iterator.call(context, obj);
var low = 0,
high = array.length;
while (low < high) {
var mid = (low + high) >>> 1;
iterator.call(context, array[mid]) < value
? low = mid + 1
: high = mid;
}
return low;
};
// Safely create a real, live array from anything iterable.
_.toArray = function(obj) {
if (!obj)
return [];
if (_.isArray(obj))
return slice.call(obj);
if (obj.length === + obj.length)
return _.map(obj, _.identity);
return _.values(obj);
};
// Return the number of elements in an object.
_.size = function(obj) {
if (obj == null)
return 0;
return (obj.length === + obj.length)
? obj.length
: _.keys(obj).length;
};
// Array Functions
// ---------------
// Get the first element of an array. Passing **n** will return the first N
// values in the array. Aliased as `head` and `take`. The **guard** check
// allows it to work with `_.map`.
_.first = _.head = _.take = function(array, n, guard) {
if (array == null)
return void 0;
return (n != null) && !guard
? slice.call(array, 0, n)
: array[0];
};
// Returns everything but the last entry of the array. Especially useful on
// the arguments object. Passing **n** will return all the values in
// the array, excluding the last N. The **guard** check allows it to work with
// `_.map`.
_.initial = function(array, n, guard) {
return slice.call(array, 0, array.length - ((n == null) || guard
? 1
: n));
};
// Get the last element of an array. Passing **n** will return the last N
// values in the array. The **guard** check allows it to work with `_.map`.
_.last = function(array, n, guard) {
if (array == null)
return void 0;
if ((n != null) && !guard) {
return slice.call(array, Math.max(array.length - n, 0));
} else {
return array[array.length - 1];
}
};
// Returns everything but the first entry of the array. Aliased as `tail` and `drop`.
// Especially useful on the arguments object. Passing an **n** will return
// the rest N values in the array. The **guard**
// check allows it to work with `_.map`.
_.rest = _.tail = _.drop = function(array, n, guard) {
return slice.call(array, (n == null) || guard
? 1
: n);
};
// Trim out all falsy values from an array.
_.compact = function(array) {
return _.filter(array, _.identity);
};
// Internal implementation of a recursive `flatten` function.
var flatten = function(input, shallow, output) {
if (shallow && _.every(input, _.isArray)) {
return concat.apply(output, input);
}
each(input, function(value) {
if (_.isArray(value) || _.isArguments(value)) {
shallow
? push.apply(output, value)
: flatten(value, shallow, output);
} else {
output.push(value);
}
});
return output;
};
// Return a completely flattened version of an array.
_.flatten = function(array, shallow) {
return flatten(array, shallow, []);
};
// Return a version of the array that does not contain the specified value(s).
_.without = function(array) {
return _.difference(array, slice.call(arguments, 1));
};
// Produce a duplicate-free version of the array. If the array has already
// been sorted, you have the option of using a faster algorithm.
// Aliased as `unique`.
_.uniq = _.unique = function(array, isSorted, iterator, context) {
if (_.isFunction(isSorted)) {
context = iterator;
iterator = isSorted;
isSorted = false;
}
var initial = iterator
? _.map(array, iterator, context)
: array;
var results = [];
var seen = [];
each(initial, function(value, index) {
if (isSorted
? (!index || seen[seen.length - 1] !== value)
: !_.contains(seen, value)) {
seen.push(value);
results.push(array[index]);
}
});
return results;
};
// Produce an array that contains the union: each distinct element from all of
// the passed-in arrays.
_.union = function() {
return _.uniq(_.flatten(arguments, true));
};
// Produce an array that contains every item shared between all the
// passed-in arrays.
_.intersection = function(array) {
var rest = slice.call(arguments, 1);
return _.filter(_.uniq(array), function(item) {
return _.every(rest, function(other) {
return _.indexOf(other, item) >= 0;
});
});
};
// Take the difference between one array and a number of other arrays.
// Only the elements present in just the first array will remain.
_.difference = function(array) {
var rest = concat.apply(ArrayProto, slice.call(arguments, 1));
return _.filter(array, function(value) {
return !_.contains(rest, value);
});
};
// Zip together multiple lists into a single array -- elements that share
// an index go together.
_.zip = function() {
return _.unzip.apply(_, slice.call(arguments));
};
// The inverse operation to `_.zip`. If given an array of pairs it
// returns an array of the paired elements split into two left and
// right element arrays, if given an array of triples it returns a
// three element array and so on. For example, `_.unzip` given
// `[['a',1],['b',2],['c',3]]` returns the array
// [['a','b','c'],[1,2,3]].
_.unzip = function() {
var length = _.max(_.pluck(arguments, "length").concat(0));
var results = new Array(length);
for (var i = 0; i < length; i++) {
results[i] = _.pluck(arguments, '' + i);
}
return results;
};
// Converts lists into objects. Pass either a single array of `[key, value]`
// pairs, or two parallel arrays of the same length -- one of keys, and one of
// the corresponding values.
_.object = function(list, values) {
if (list == null)
return {};
var result = {};
for (var i = 0, l = list.length; i < l; i++) {
if (values) {
result[list[i]] = values[i];
} else {
result[list[i][0]] = list[i][1];
}
}
return result;
};
// If the browser doesn't supply us with indexOf (I'm looking at you, **MSIE**),
// we need this function. Return the position of the first occurrence of an
// item in an array, or -1 if the item is not included in the array.
// Delegates to **ECMAScript 5**'s native `indexOf` if available.
// If the array is large and already in sort order, pass `true`
// for **isSorted** to use binary search.
_.indexOf = function(array, item, isSorted) {
if (array == null)
return -1;
var i = 0,
l = array.length;
if (isSorted) {
if (typeof isSorted == 'number') {
i = (isSorted < 0
? Math.max(0, l + isSorted)
: isSorted);
} else {
i = _.sortedIndex(array, item);
return array[i] === item
? i
: -1;
}
}
if (nativeIndexOf && array.indexOf === nativeIndexOf)
return array.indexOf(item, isSorted);
for (; i < l; i++)
if (array[i] === item)
return i;
return -1;
};
// Delegates to **ECMAScript 5**'s native `lastIndexOf` if available.
_.lastIndexOf = function(array, item, from) {
if (array == null)
return -1;
var hasIndex = from != null;
if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) {
return hasIndex
? array.lastIndexOf(item, from)
: array.lastIndexOf(item);
}
var i = (hasIndex
? from
: array.length);
while (i--)
if (array[i] === item)
return i;
return -1;
};
// Generate an integer Array containing an arithmetic progression. A port of
// the native Python `range()` function. See
// [the Python documentation](http://docs.python.org/library/functions.html#range).
_.range = function(start, stop, step) {
if (arguments.length <= 1) {
stop = start || 0;
start = 0;
}
step = arguments[2] || 1;
var len = Math.max(Math.ceil((stop - start) / step), 0);
var idx = 0;
var range = new Array(len);
while (idx < len) {
range[idx++] = start;
start += step;
}
return range;
};
// Function (ahem) Functions
// ------------------
// Reusable constructor function for prototype setting.
var ctor = function() {};
// Create a function bound to a given object (assigning `this`, and arguments,
// optionally). Delegates to **ECMAScript 5**'s native `Function.bind` if
// available.
_.bind = function(func, context) {
var args,
bound;
if (nativeBind && func.bind === nativeBind)
return nativeBind.apply(func, slice.call(arguments, 1));
if (!_.isFunction(func))
throw new TypeError;
args = slice.call(arguments, 2);
return bound = function() {
if (!(this instanceof bound))
return func.apply(context, args.concat(slice.call(arguments)));
ctor.prototype = func.prototype;
var self = new ctor;
ctor.prototype = null;
var result = func.apply(self, args.concat(slice.call(arguments)));
if (Object(result) === result)
return result;
return self;
};
};
// Partially apply a function by creating a version that has had some of its
// arguments pre-filled, without changing its dynamic `this` context.
_.partial = function(func) {
var args = slice.call(arguments, 1);
return function() {
return func.apply(this, args.concat(slice.call(arguments)));
};
};
// Bind all of an object's methods to that object. Useful for ensuring that
// all callbacks defined on an object belong to it.
_.bindAll = function(obj) {
var funcs = slice.call(arguments, 1);
if (funcs.length === 0)
throw new Error("bindAll must be passed function names");
each(funcs, function(f) {
obj[f] = _.bind(obj[f], obj);
});
return obj;
};
// Memoize an expensive function by storing its results.
_.memoize = function(func, hasher) {
var memo = {};
hasher || (hasher = _.identity);
return function() {
var key = hasher.apply(this, arguments);
return _.has(memo, key)
? memo[key]
: (memo[key] = func.apply(this, arguments));
};
};
// Delays a function for the given number of milliseconds, and then calls
// it with the arguments supplied.
_.delay = function(func, wait) {
var args = slice.call(arguments, 2);
return setTimeout(function() {
return func.apply(null, args);
}, wait);
};
// Defers a function, scheduling it to run after the current call stack has
// cleared.
_.defer = function(func) {
return _.delay.apply(_, [func, 1].concat(slice.call(arguments, 1)));
};
// Returns a function, that, when invoked, will only be triggered at most once
// during a given window of time. Normally, the throttled function will run
// as much as it can, without ever going more than once per `wait` duration;
// but if you'd like to disable the execution on the leading edge, pass
// `{leading: false}`. To disable execution on the trailing edge, ditto.
_.throttle = function(func, wait, options) {
var context,
args,
result;
var timeout = null;
var previous = 0;
options || (options = {});
var later = function() {
previous = new Date;
timeout = null;
result = func.apply(context, args);
};
return function() {
var now = new Date;
if (!previous && options.leading === false)
previous = now;
var remaining = wait - (now - previous);
context = this;
args = arguments;
if (remaining <= 0) {
clearTimeout(timeout);
timeout = null;
previous = now;
result = func.apply(context, args);
} else if (!timeout && options.trailing !== false) {
timeout = setTimeout(later, remaining);
}
return result;
};
};
// Returns a function, that, as long as it continues to be invoked, will not
// be triggered. The function will be called after it stops being called for
// N milliseconds. If `immediate` is passed, trigger the function on the
// leading edge, instead of the trailing.
_.debounce = function(func, wait, immediate) {
var result;
var timeout = null;
return function() {
var context = this,
args = arguments;
var later = function() {
timeout = null;
if (!immediate)
result = func.apply(context, args);
};
var callNow = immediate && !timeout;
clearTimeout(timeout);
timeout = setTimeout(later, wait);
if (callNow)
result = func.apply(context, args);
return result;
};
};
// Returns a function that will be executed at most one time, no matter how
// often you call it. Useful for lazy initialization.
_.once = function(func) {
var ran = false,
memo;
return function() {
if (ran)
return memo;
ran = true;
memo = func.apply(this, arguments);
func = null;
return memo;
};
};
// Returns the first function passed as an argument to the second,
// allowing you to adjust arguments, run code before and after, and
// conditionally execute the original function.
_.wrap = function(func, wrapper) {
return function() {
var args = [func];
push.apply(args, arguments);
return wrapper.apply(this, args);
};
};
// Returns a function that is the composition of a list of functions, each
// consuming the return value of the function that follows.
_.compose = function() {
var funcs = arguments;
return function() {
var args = arguments;
for (var i = funcs.length - 1; i >= 0; i--) {
args = [funcs[i].apply(this, args)];
}
return args[0];
};
};
// Returns a function that will only be executed after being called N times.
_.after = function(times, func) {
return function() {
if (--times < 1) {
return func.apply(this, arguments);
}
};
};
// Object Functions
// ----------------
// Retrieve the names of an object's properties.
// Delegates to **ECMAScript 5**'s native `Object.keys`
_.keys = nativeKeys || function(obj) {
if (obj !== Object(obj))
throw new TypeError('Invalid object');
var keys = [];
for (var key in obj)
if (_.has(obj, key))
keys.push(key);
return keys;
};
// Retrieve the values of an object's properties.
_.values = function(obj) {
var values = [];
for (var key in obj)
if (_.has(obj, key))
values.push(obj[key]);
return values;
};
// Convert an object into a list of `[key, value]` pairs.
_.pairs = function(obj) {
var pairs = [];
for (var key in obj)
if (_.has(obj, key))
pairs.push([key, obj[key]]);
return pairs;
};
// Invert the keys and values of an object. The values must be serializable.
_.invert = function(obj) {
var result = {};
for (var key in obj)
if (_.has(obj, key))
result[obj[key]] = key;
return result;
};
// 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 a given object with all the properties in passed-in object(s).
_.extend = function(obj) {
each(slice.call(arguments, 1), function(source) {
if (source) {
for (var prop in source) {
obj[prop] = source[prop];
}
}
});
return obj;
};
// Return a copy of the object only containing the whitelisted properties.
_.pick = function(obj) {
var copy = {};
var keys = concat.apply(ArrayProto, slice.call(arguments, 1));
each(keys, function(key) {
if (key in obj)
copy[key] = obj[key];
}
);
return copy;
};
// Return a copy of the object without the blacklisted properties.
_.omit = function(obj) {
var copy = {};
var keys = concat.apply(ArrayProto, slice.call(arguments, 1));
for (var key in obj) {
if (!_.contains(keys, key))
copy[key] = obj[key];
}
return copy;
};
// Fill in a given object with default properties.
_.defaults = function(obj) {
each(slice.call(arguments, 1), function(source) {
if (source) {
for (var prop in source) {
if (obj[prop] === void 0)
obj[prop] = source[prop];
}
}
});
return obj;
};
// Create a (shallow-cloned) duplicate of an object.
_.clone = function(obj) {
if (!_.isObject(obj))
return obj;
return _.isArray(obj)
? obj.slice()
: _.extend({}, obj);
};
// 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) {
interceptor(obj);
return obj;
};
// 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).
if (a === b)
return a !== 0 || 1 / a == 1 / b;
// A strict comparison is necessary because `null == undefined`.
if (a == null || b == null)
return a === b;
// Unwrap any wrapped objects.
if (a instanceof _)
a = a._wrapped;
if (b instanceof _)
b = b._wrapped;
// Compare `[[Class]]` names.
var className = toString.call(a);
if (className != toString.call(b))
return false;
switch (className) {
// Strings, numbers, dates, and booleans are compared by value.
case '[object String]':
// Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
// equivalent to `new String("5")`.
return a == String(b);
case '[object Number]':
// `NaN`s are equivalent, but non-reflexive. An `egal` comparison is performed for
// other numeric values.
return a != + a
? b != + b
: (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.
return + a == + b;
// RegExps are compared by their source patterns and flags.
case '[object RegExp]':
return a.source == b.source && a.global == b.global && a.multiline == b.multiline && a.ignoreCase == b.ignoreCase;
}
if (typeof a != 'object' || typeof b != 'object')
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`.
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;
}
// Objects with different constructors are not equivalent, but `Object`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))) {
return false;
}
// Add the first object to the stack of traversed objects.
aStack.push(a);
bStack.push(b);
var size = 0,
result = true;
// Recursively compare objects and arrays.
if (className == '[object Array]') {
// Compare array lengths to determine if a deep comparison is necessary.
size = a.length;
result = size == b.length;
if (result) {
// Deep compare the contents, ignoring non-numeric properties.
while (size--) {
if (!(result = eq(a[size], b[size], aStack, bStack)))
break;
}
}
} else {
// Deep compare objects.
for (var key in a) {
if (_.has(a, key)) {
// Count the expected number of properties.
size++;
// Deep compare each member.
if (!(result = _.has(b, key) && eq(a[key], b[key], aStack, bStack)))
break;
}
}
// Ensure that both objects contain the same number of properties.
if (result) {
for (key in b) {
if (_.has(b, key) && !(size--))
break;
}
result = !size;
}
}
// Remove the first object from the stack of traversed objects.
aStack.pop();
bStack.pop();
return result;
};
// Perform a deep comparison to check if two objects are equal.
_.isEqual = function(a, b) {
return eq(a, b, [], []);
};
// 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 (_.isArray(obj) || _.isString(obj))
return obj.length === 0;
for (var key in obj)
if (_.has(obj, key))
return false;
return true;
};
// Is a given value a DOM element?
_.isElement = function(obj) {
return !!(obj && obj.nodeType === 1);
};
// Is a given value an array?
// Delegates to ECMA5's native Array.isArray
_.isArray = nativeIsArray || function(obj) {
return toString.call(obj) == '[object Array]';
};
// Is a given variable an object?
_.isObject = function(obj) {
return obj === Object(obj);
};
// Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp.
each([
'Arguments',
'Function',
'String',
'Number',
'Date',
'RegExp'
], function(name) {
_['is' + name] = function(obj) {
return toString.call(obj) == '[object ' + name + ']';
};
});
// Define a fallback version of the method in browsers (ahem, IE), where
// there isn't any inspectable "Arguments" type.
if (!_.isArguments(arguments)) {
_.isArguments = function(obj) {
return !!(obj && _.has(obj, 'callee'));
};
}
// Optimize `isFunction` if appropriate.
if (typeof(/./) !== 'function') {
_.isFunction = function(obj) {
return typeof obj === 'function';
};
}
// Is a given object a finite number?
_.isFinite = function(obj) {
return isFinite(obj) && !isNaN(parseFloat(obj));
};
// Is the given value `NaN`? (NaN is the only number which does not equal itself).
_.isNaN = function(obj) {
return _.isNumber(obj) && obj != + obj;
};
// Is a given value a boolean?
_.isBoolean = function(obj) {
return obj === true || obj === false || toString.call(obj) == '[object Boolean]';
};
// Is a given value equal to null?
_.isNull = function(obj) {
return obj === null;
};
// Is a given variable undefined?
_.isUndefined = function(obj) {
return obj === void 0;
};
// 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 hasOwnProperty.call(obj, key);
};
// Utility Functions
// -----------------
// 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;
};
// Keep the identity function around for default iterators.
_.identity = function(value) {
return value;
};
// Run a function **n** times.
_.times = function(n, iterator, context) {
var accum = Array(Math.max(0, n));
for (var i = 0; i < n; i++)
accum[i] = iterator.call(context, i);
return accum;
};
// 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));
};
// List of HTML entities for escaping.
var entityMap = {
escape: {
'&': '&',
'<': '<',
'>': '>',
'"': '"',
"'": ''',
'/': '/'
}
};
entityMap.unescape = _.invert(entityMap.escape);
// Regexes containing the keys and values listed immediately above.
var entityRegexes = {
escape: new RegExp('[' + _.keys(entityMap.escape).join('') + ']', 'g'),
unescape: new RegExp('(' + _.keys(entityMap.unescape).join('|') + ')', 'g')
};
// Functions for escaping and unescaping strings to/from HTML interpolation.
_.each([
'escape', 'unescape'
], function(method) {
_[method] = function(string) {
if (string == null)
return '';
return ('' + string).replace(entityRegexes[method], function(match) {
return entityMap[method][match];
});
};
});
// 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) {
if (object == null)
return void 0;
var value = object[property];
return _.isFunction(value)
? value.call(object)
: value;
};
// 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.call(this, func.apply(_, args));
};
});
};
// 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',
'\t': 't',
'\u2028': 'u2028',
'\u2029': 'u2029'
};
var escaper = /\\|'|\r|\n|\t|\u2028|\u2029/g;
// JavaScript micro-templating, similar to John Resig's implementation.
// Underscore templating handles arbitrary delimiters, preserves whitespace,
// and correctly escapes quotes within interpolated code.
_.template = function(text, data, settings) {
var render;
settings = _.defaults({}, settings, _.templateSettings);
// Combine delimiters into one regular expression via alternation.
var matcher = new 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, function(match) {
return '\\' + escapes[match];
});
if (escape) {
source += "'+\n((__t=(" + escape + "))==null?'':_.escape(__t))+\n'";
}
if (interpolate) {
source += "'+\n((__t=(" + interpolate + "))==null?'':__t)+\n'";
}
if (evaluate) {
source += "';\n" + evaluate + "\n__p+='";
}
index = offset + match.length;
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 {
render = new Function(settings.variable || 'obj', '_', source);
} catch (e) {
e.source = source;
throw e;
}
if (data)
return render(data, _);
var template = function(data) {
return render.call(this, data, _);
};
// Provide the compiled function source as a convenience for precompilation.
template.source = 'function(' + (settings.variable || 'obj') + '){\n' + source + '}';
return template;
};
// Add a "chain" function, which will delegate to the wrapper.
_.chain = function(obj) {
return _(obj).chain();
};
// 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(obj) {
return this._chain
? _(obj).chain()
: obj;
};
// Add all of the Underscore functions to the wrapper object.
_.mixin(_);
// 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.call(this, obj);
};
});
// Add all accessor Array functions to the wrapper.
each([
'concat', 'join', 'slice'
], function(name) {
var method = ArrayProto[name];
_.prototype[name] = function() {
return result.call(this, method.apply(this._wrapped, arguments));
};
});
_.extend(_.prototype, {
// Start chaining a wrapped Underscore object.
chain: function() {
this._chain = true;
return this;
},
// Extracts the result from a wrapped and chained object.
value: function() {
return this._wrapped;
}
});
}).call(this);