Código fuente de WordPress - trunk (underscore-1.4.4.js)

1	//     Underscore.js 1.4.4
2	//     http://underscorejs.org
3	//     (c) 2009-2013 Jeremy Ashkenas, DocumentCloud Inc.
4	//     Underscore may be freely distributed under the MIT license.
5	
6	(function() {
7	
8	  // Baseline setup
9	  // --------------
10	
11	  // Establish the root object, `window` in the browser, or `global` on the server.
12	  var root = this;
13	
14	  // Save the previous value of the `_` variable.
15	  var previousUnderscore = root._;
16	
17	  // Establish the object that gets returned to break out of a loop iteration.
18	  var breaker = {};
19	
20	  // Save bytes in the minified (but not gzipped) version:
21	  var ArrayProto = Array.prototype, ObjProto = Object.prototype, FuncProto = Function.prototype;
22	
23	  // Create quick reference variables for speed access to core prototypes.
24	  var push             = ArrayProto.push,
25	      slice            = ArrayProto.slice,
26	      concat           = ArrayProto.concat,
27	      toString         = ObjProto.toString,
28	      hasOwnProperty   = ObjProto.hasOwnProperty;
29	
30	  // All **ECMAScript 5** native function implementations that we hope to use
31	  // are declared here.
32	  var
33	    nativeForEach      = ArrayProto.forEach,
34	    nativeMap          = ArrayProto.map,
35	    nativeReduce       = ArrayProto.reduce,
36	    nativeReduceRight  = ArrayProto.reduceRight,
37	    nativeFilter       = ArrayProto.filter,
38	    nativeEvery        = ArrayProto.every,
39	    nativeSome         = ArrayProto.some,
40	    nativeIndexOf      = ArrayProto.indexOf,
41	    nativeLastIndexOf  = ArrayProto.lastIndexOf,
42	    nativeIsArray      = Array.isArray,
43	    nativeKeys         = Object.keys,
44	    nativeBind         = FuncProto.bind;
45	
46	  // Create a safe reference to the Underscore object for use below.
47	  var _ = function(obj) {
48	    if (obj instanceof _) return obj;
49	    if (!(this instanceof _)) return new _(obj);
50	    this._wrapped = obj;
51	  };
52	
53	  // Export the Underscore object for **Node.js**, with
54	  // backwards-compatibility for the old `require()` API. If we're in
55	  // the browser, add `_` as a global object via a string identifier,
56	  // for Closure Compiler "advanced" mode.
57	  if (typeof exports !== 'undefined') {
58	    if (typeof module !== 'undefined' && module.exports) {
59	      exports = module.exports = _;
60	    }
61	    exports._ = _;
62	  } else {
63	    root._ = _;
64	  }
65	
66	  // Current version.
67	  _.VERSION = '1.4.4';
68	
69	  // Collection Functions
70	  // --------------------
71	
72	  // The cornerstone, an `each` implementation, aka `forEach`.
73	  // Handles objects with the built-in `forEach`, arrays, and raw objects.
74	  // Delegates to **ECMAScript 5**'s native `forEach` if available.
75	  var each = _.each = _.forEach = function(obj, iterator, context) {
76	    if (obj == null) return;
77	    if (nativeForEach && obj.forEach === nativeForEach) {
78	      obj.forEach(iterator, context);
79	    } else if (obj.length === +obj.length) {
80	      for (var i = 0, l = obj.length; i < l; i++) {
81	        if (iterator.call(context, obj[i], i, obj) === breaker) return;
82	      }
83	    } else {
84	      for (var key in obj) {
85	        if (_.has(obj, key)) {
86	          if (iterator.call(context, obj[key], key, obj) === breaker) return;
87	        }
88	      }
89	    }
90	  };
91	
92	  // Return the results of applying the iterator to each element.
93	  // Delegates to **ECMAScript 5**'s native `map` if available.
94	  _.map = _.collect = function(obj, iterator, context) {
95	    var results = [];
96	    if (obj == null) return results;
97	    if (nativeMap && obj.map === nativeMap) return obj.map(iterator, context);
98	    each(obj, function(value, index, list) {
99	      results[results.length] = iterator.call(context, value, index, list);
100	    });
101	    return results;
102	  };
103	
104	  var reduceError = 'Reduce of empty array with no initial value';
105	
106	  // **Reduce** builds up a single result from a list of values, aka `inject`,
107	  // or `foldl`. Delegates to **ECMAScript 5**'s native `reduce` if available.
108	  _.reduce = _.foldl = _.inject = function(obj, iterator, memo, context) {
109	    var initial = arguments.length > 2;
110	    if (obj == null) obj = [];
111	    if (nativeReduce && obj.reduce === nativeReduce) {
112	      if (context) iterator = _.bind(iterator, context);
113	      return initial ? obj.reduce(iterator, memo) : obj.reduce(iterator);
114	    }
115	    each(obj, function(value, index, list) {
116	      if (!initial) {
117	        memo = value;
118	        initial = true;
119	      } else {
120	        memo = iterator.call(context, memo, value, index, list);
121	      }
122	    });
123	    if (!initial) throw new TypeError(reduceError);
124	    return memo;
125	  };
126	
127	  // The right-associative version of reduce, also known as `foldr`.
128	  // Delegates to **ECMAScript 5**'s native `reduceRight` if available.
129	  _.reduceRight = _.foldr = function(obj, iterator, memo, context) {
130	    var initial = arguments.length > 2;
131	    if (obj == null) obj = [];
132	    if (nativeReduceRight && obj.reduceRight === nativeReduceRight) {
133	      if (context) iterator = _.bind(iterator, context);
134	      return initial ? obj.reduceRight(iterator, memo) : obj.reduceRight(iterator);
135	    }
136	    var length = obj.length;
137	    if (length !== +length) {
138	      var keys = _.keys(obj);
139	      length = keys.length;
140	    }
141	    each(obj, function(value, index, list) {
142	      index = keys ? keys[--length] : --length;
143	      if (!initial) {
144	        memo = obj[index];
145	        initial = true;
146	      } else {
147	        memo = iterator.call(context, memo, obj[index], index, list);
148	      }
149	    });
150	    if (!initial) throw new TypeError(reduceError);
151	    return memo;
152	  };
153	
154	  // Return the first value which passes a truth test. Aliased as `detect`.
155	  _.find = _.detect = function(obj, iterator, context) {
156	    var result;
157	    any(obj, function(value, index, list) {
158	      if (iterator.call(context, value, index, list)) {
159	        result = value;
160	        return true;
161	      }
162	    });
163	    return result;
164	  };
165	
166	  // Return all the elements that pass a truth test.
167	  // Delegates to **ECMAScript 5**'s native `filter` if available.
168	  // Aliased as `select`.
169	  _.filter = _.select = function(obj, iterator, context) {
170	    var results = [];
171	    if (obj == null) return results;
172	    if (nativeFilter && obj.filter === nativeFilter) return obj.filter(iterator, context);
173	    each(obj, function(value, index, list) {
174	      if (iterator.call(context, value, index, list)) results[results.length] = value;
175	    });
176	    return results;
177	  };
178	
179	  // Return all the elements for which a truth test fails.
180	  _.reject = function(obj, iterator, context) {
181	    return _.filter(obj, function(value, index, list) {
182	      return !iterator.call(context, value, index, list);
183	    }, context);
184	  };
185	
186	  // Determine whether all of the elements match a truth test.
187	  // Delegates to **ECMAScript 5**'s native `every` if available.
188	  // Aliased as `all`.
189	  _.every = _.all = function(obj, iterator, context) {
190	    iterator || (iterator = _.identity);
191	    var result = true;
192	    if (obj == null) return result;
193	    if (nativeEvery && obj.every === nativeEvery) return obj.every(iterator, context);
194	    each(obj, function(value, index, list) {
195	      if (!(result = result && iterator.call(context, value, index, list))) return breaker;
196	    });
197	    return !!result;
198	  };
199	
200	  // Determine if at least one element in the object matches a truth test.
201	  // Delegates to **ECMAScript 5**'s native `some` if available.
202	  // Aliased as `any`.
203	  var any = _.some = _.any = function(obj, iterator, context) {
204	    iterator || (iterator = _.identity);
205	    var result = false;
206	    if (obj == null) return result;
207	    if (nativeSome && obj.some === nativeSome) return obj.some(iterator, context);
208	    each(obj, function(value, index, list) {
209	      if (result || (result = iterator.call(context, value, index, list))) return breaker;
210	    });
211	    return !!result;
212	  };
213	
214	  // Determine if the array or object contains a given value (using `===`).
215	  // Aliased as `include`.
216	  _.contains = _.include = function(obj, target) {
217	    if (obj == null) return false;
218	    if (nativeIndexOf && obj.indexOf === nativeIndexOf) return obj.indexOf(target) != -1;
219	    return any(obj, function(value) {
220	      return value === target;
221	    });
222	  };
223	
224	  // Invoke a method (with arguments) on every item in a collection.
225	  _.invoke = function(obj, method) {
226	    var args = slice.call(arguments, 2);
227	    var isFunc = _.isFunction(method);
228	    return _.map(obj, function(value) {
229	      return (isFunc ? method : value[method]).apply(value, args);
230	    });
231	  };
232	
233	  // Convenience version of a common use case of `map`: fetching a property.
234	  _.pluck = function(obj, key) {
235	    return _.map(obj, function(value){ return value[key]; });
236	  };
237	
238	  // Convenience version of a common use case of `filter`: selecting only objects
239	  // containing specific `key:value` pairs.
240	  _.where = function(obj, attrs, first) {
241	    if (_.isEmpty(attrs)) return first ? null : [];
242	    return _[first ? 'find' : 'filter'](obj, function(value) {
243	      for (var key in attrs) {
244	        if (attrs[key] !== value[key]) return false;
245	      }
246	      return true;
247	    });
248	  };
249	
250	  // Convenience version of a common use case of `find`: getting the first object
251	  // containing specific `key:value` pairs.
252	  _.findWhere = function(obj, attrs) {
253	    return _.where(obj, attrs, true);
254	  };
255	
256	  // Return the maximum element or (element-based computation).
257	  // Can't optimize arrays of integers longer than 65,535 elements.
258	  // See: https://bugs.webkit.org/show_bug.cgi?id=80797
259	  _.max = function(obj, iterator, context) {
260	    if (!iterator && _.isArray(obj) && obj[0] === +obj[0] && obj.length < 65535) {
261	      return Math.max.apply(Math, obj);
262	    }
263	    if (!iterator && _.isEmpty(obj)) return -Infinity;
264	    var result = {computed : -Infinity, value: -Infinity};
265	    each(obj, function(value, index, list) {
266	      var computed = iterator ? iterator.call(context, value, index, list) : value;
267	      computed >= result.computed && (result = {value : value, computed : computed});
268	    });
269	    return result.value;
270	  };
271	
272	  // Return the minimum element (or element-based computation).
273	  _.min = function(obj, iterator, context) {
274	    if (!iterator && _.isArray(obj) && obj[0] === +obj[0] && obj.length < 65535) {
275	      return Math.min.apply(Math, obj);
276	    }
277	    if (!iterator && _.isEmpty(obj)) return Infinity;
278	    var result = {computed : Infinity, value: Infinity};
279	    each(obj, function(value, index, list) {
280	      var computed = iterator ? iterator.call(context, value, index, list) : value;
281	      computed < result.computed && (result = {value : value, computed : computed});
282	    });
283	    return result.value;
284	  };
285	
286	  // Shuffle an array.
287	  _.shuffle = function(obj) {
288	    var rand;
289	    var index = 0;
290	    var shuffled = [];
291	    each(obj, function(value) {
292	      rand = _.random(index++);
293	      shuffled[index - 1] = shuffled[rand];
294	      shuffled[rand] = value;
295	    });
296	    return shuffled;
297	  };
298	
299	  // An internal function to generate lookup iterators.
300	  var lookupIterator = function(value) {
301	    return _.isFunction(value) ? value : function(obj){ return obj[value]; };
302	  };
303	
304	  // Sort the object's values by a criterion produced by an iterator.
305	  _.sortBy = function(obj, value, context) {
306	    var iterator = lookupIterator(value);
307	    return _.pluck(_.map(obj, function(value, index, list) {
308	      return {
309	        value : value,
310	        index : index,
311	        criteria : iterator.call(context, value, index, list)
312	      };
313	    }).sort(function(left, right) {
314	      var a = left.criteria;
315	      var b = right.criteria;
316	      if (a !== b) {
317	        if (a > b || a === void 0) return 1;
318	        if (a < b || b === void 0) return -1;
319	      }
320	      return left.index < right.index ? -1 : 1;
321	    }), 'value');
322	  };
323	
324	  // An internal function used for aggregate "group by" operations.
325	  var group = function(obj, value, context, behavior) {
326	    var result = {};
327	    var iterator = lookupIterator(value || _.identity);
328	    each(obj, function(value, index) {
329	      var key = iterator.call(context, value, index, obj);
330	      behavior(result, key, value);
331	    });
332	    return result;
333	  };
334	
335	  // Groups the object's values by a criterion. Pass either a string attribute
336	  // to group by, or a function that returns the criterion.
337	  _.groupBy = function(obj, value, context) {
338	    return group(obj, value, context, function(result, key, value) {
339	      (_.has(result, key) ? result[key] : (result[key] = [])).push(value);
340	    });
341	  };
342	
343	  // Counts instances of an object that group by a certain criterion. Pass
344	  // either a string attribute to count by, or a function that returns the
345	  // criterion.
346	  _.countBy = function(obj, value, context) {
347	    return group(obj, value, context, function(result, key) {
348	      if (!_.has(result, key)) result[key] = 0;
349	      result[key]++;
350	    });
351	  };
352	
353	  // Use a comparator function to figure out the smallest index at which
354	  // an object should be inserted so as to maintain order. Uses binary search.
355	  _.sortedIndex = function(array, obj, iterator, context) {
356	    iterator = iterator == null ? _.identity : lookupIterator(iterator);
357	    var value = iterator.call(context, obj);
358	    var low = 0, high = array.length;
359	    while (low < high) {
360	      var mid = (low + high) >>> 1;
361	      iterator.call(context, array[mid]) < value ? low = mid + 1 : high = mid;
362	    }
363	    return low;
364	  };
365	
366	  // Safely convert anything iterable into a real, live array.
367	  _.toArray = function(obj) {
368	    if (!obj) return [];
369	    if (_.isArray(obj)) return slice.call(obj);
370	    if (obj.length === +obj.length) return _.map(obj, _.identity);
371	    return _.values(obj);
372	  };
373	
374	  // Return the number of elements in an object.
375	  _.size = function(obj) {
376	    if (obj == null) return 0;
377	    return (obj.length === +obj.length) ? obj.length : _.keys(obj).length;
378	  };
379	
380	  // Array Functions
381	  // ---------------
382	
383	  // Get the first element of an array. Passing **n** will return the first N
384	  // values in the array. Aliased as `head` and `take`. The **guard** check
385	  // allows it to work with `_.map`.
386	  _.first = _.head = _.take = function(array, n, guard) {
387	    if (array == null) return void 0;
388	    return (n != null) && !guard ? slice.call(array, 0, n) : array[0];
389	  };
390	
391	  // Returns everything but the last entry of the array. Especially useful on
392	  // the arguments object. Passing **n** will return all the values in
393	  // the array, excluding the last N. The **guard** check allows it to work with
394	  // `_.map`.
395	  _.initial = function(array, n, guard) {
396	    return slice.call(array, 0, array.length - ((n == null) || guard ? 1 : n));
397	  };
398	
399	  // Get the last element of an array. Passing **n** will return the last N
400	  // values in the array. The **guard** check allows it to work with `_.map`.
401	  _.last = function(array, n, guard) {
402	    if (array == null) return void 0;
403	    if ((n != null) && !guard) {
404	      return slice.call(array, Math.max(array.length - n, 0));
405	    } else {
406	      return array[array.length - 1];
407	    }
408	  };
409	
410	  // Returns everything but the first entry of the array. Aliased as `tail` and `drop`.
411	  // Especially useful on the arguments object. Passing an **n** will return
412	  // the rest N values in the array. The **guard**
413	  // check allows it to work with `_.map`.
414	  _.rest = _.tail = _.drop = function(array, n, guard) {
415	    return slice.call(array, (n == null) || guard ? 1 : n);
416	  };
417	
418	  // Trim out all falsy values from an array.
419	  _.compact = function(array) {
420	    return _.filter(array, _.identity);
421	  };
422	
423	  // Internal implementation of a recursive `flatten` function.
424	  var flatten = function(input, shallow, output) {
425	    each(input, function(value) {
426	      if (_.isArray(value)) {
427	        shallow ? push.apply(output, value) : flatten(value, shallow, output);
428	      } else {
429	        output.push(value);
430	      }
431	    });
432	    return output;
433	  };
434	
435	  // Return a completely flattened version of an array.
436	  _.flatten = function(array, shallow) {
437	    return flatten(array, shallow, []);
438	  };
439	
440	  // Return a version of the array that does not contain the specified value(s).
441	  _.without = function(array) {
442	    return _.difference(array, slice.call(arguments, 1));
443	  };
444	
445	  // Produce a duplicate-free version of the array. If the array has already
446	  // been sorted, you have the option of using a faster algorithm.
447	  // Aliased as `unique`.
448	  _.uniq = _.unique = function(array, isSorted, iterator, context) {
449	    if (_.isFunction(isSorted)) {
450	      context = iterator;
451	      iterator = isSorted;
452	      isSorted = false;
453	    }
454	    var initial = iterator ? _.map(array, iterator, context) : array;
455	    var results = [];
456	    var seen = [];
457	    each(initial, function(value, index) {
458	      if (isSorted ? (!index || seen[seen.length - 1] !== value) : !_.contains(seen, value)) {
459	        seen.push(value);
460	        results.push(array[index]);
461	      }
462	    });
463	    return results;
464	  };
465	
466	  // Produce an array that contains the union: each distinct element from all of
467	  // the passed-in arrays.
468	  _.union = function() {
469	    return _.uniq(concat.apply(ArrayProto, arguments));
470	  };
471	
472	  // Produce an array that contains every item shared between all the
473	  // passed-in arrays.
474	  _.intersection = function(array) {
475	    var rest = slice.call(arguments, 1);
476	    return _.filter(_.uniq(array), function(item) {
477	      return _.every(rest, function(other) {
478	        return _.indexOf(other, item) >= 0;
479	      });
480	    });
481	  };
482	
483	  // Take the difference between one array and a number of other arrays.
484	  // Only the elements present in just the first array will remain.
485	  _.difference = function(array) {
486	    var rest = concat.apply(ArrayProto, slice.call(arguments, 1));
487	    return _.filter(array, function(value){ return !_.contains(rest, value); });
488	  };
489	
490	  // Zip together multiple lists into a single array -- elements that share
491	  // an index go together.
492	  _.zip = function() {
493	    var args = slice.call(arguments);
494	    var length = _.max(_.pluck(args, 'length'));
495	    var results = new Array(length);
496	    for (var i = 0; i < length; i++) {
497	      results[i] = _.pluck(args, "" + i);
498	    }
499	    return results;
500	  };
501	
502	  // Converts lists into objects. Pass either a single array of `[key, value]`
503	  // pairs, or two parallel arrays of the same length -- one of keys, and one of
504	  // the corresponding values.
505	  _.object = function(list, values) {
506	    if (list == null) return {};
507	    var result = {};
508	    for (var i = 0, l = list.length; i < l; i++) {
509	      if (values) {
510	        result[list[i]] = values[i];
511	      } else {
512	        result[list[i][0]] = list[i][1];
513	      }
514	    }
515	    return result;
516	  };
517	
518	  // If the browser doesn't supply us with indexOf (I'm looking at you, **MSIE**),
519	  // we need this function. Return the position of the first occurrence of an
520	  // item in an array, or -1 if the item is not included in the array.
521	  // Delegates to **ECMAScript 5**'s native `indexOf` if available.
522	  // If the array is large and already in sort order, pass `true`
523	  // for **isSorted** to use binary search.
524	  _.indexOf = function(array, item, isSorted) {
525	    if (array == null) return -1;
526	    var i = 0, l = array.length;
527	    if (isSorted) {
528	      if (typeof isSorted == 'number') {
529	        i = (isSorted < 0 ? Math.max(0, l + isSorted) : isSorted);
530	      } else {
531	        i = _.sortedIndex(array, item);
532	        return array[i] === item ? i : -1;
533	      }
534	    }
535	    if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item, isSorted);
536	    for (; i < l; i++) if (array[i] === item) return i;
537	    return -1;
538	  };
539	
540	  // Delegates to **ECMAScript 5**'s native `lastIndexOf` if available.
541	  _.lastIndexOf = function(array, item, from) {
542	    if (array == null) return -1;
543	    var hasIndex = from != null;
544	    if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) {
545	      return hasIndex ? array.lastIndexOf(item, from) : array.lastIndexOf(item);
546	    }
547	    var i = (hasIndex ? from : array.length);
548	    while (i--) if (array[i] === item) return i;
549	    return -1;
550	  };
551	
552	  // Generate an integer Array containing an arithmetic progression. A port of
553	  // the native Python `range()` function. See
554	  // [the Python documentation](http://docs.python.org/library/functions.html#range).
555	  _.range = function(start, stop, step) {
556	    if (arguments.length <= 1) {
557	      stop = start || 0;
558	      start = 0;
559	    }
560	    step = arguments[2] || 1;
561	
562	    var len = Math.max(Math.ceil((stop - start) / step), 0);
563	    var idx = 0;
564	    var range = new Array(len);
565	
566	    while(idx < len) {
567	      range[idx++] = start;
568	      start += step;
569	    }
570	
571	    return range;
572	  };
573	
574	  // Function (ahem) Functions
575	  // ------------------
576	
577	  // Create a function bound to a given object (assigning `this`, and arguments,
578	  // optionally). Delegates to **ECMAScript 5**'s native `Function.bind` if
579	  // available.
580	  _.bind = function(func, context) {
581	    if (func.bind === nativeBind && nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
582	    var args = slice.call(arguments, 2);
583	    return function() {
584	      return func.apply(context, args.concat(slice.call(arguments)));
585	    };
586	  };
587	
588	  // Partially apply a function by creating a version that has had some of its
589	  // arguments pre-filled, without changing its dynamic `this` context.
590	  _.partial = function(func) {
591	    var args = slice.call(arguments, 1);
592	    return function() {
593	      return func.apply(this, args.concat(slice.call(arguments)));
594	    };
595	  };
596	
597	  // Bind all of an object's methods to that object. Useful for ensuring that
598	  // all callbacks defined on an object belong to it.
599	  _.bindAll = function(obj) {
600	    var funcs = slice.call(arguments, 1);
601	    if (funcs.length === 0) funcs = _.functions(obj);
602	    each(funcs, function(f) { obj[f] = _.bind(obj[f], obj); });
603	    return obj;
604	  };
605	
606	  // Memoize an expensive function by storing its results.
607	  _.memoize = function(func, hasher) {
608	    var memo = {};
609	    hasher || (hasher = _.identity);
610	    return function() {
611	      var key = hasher.apply(this, arguments);
612	      return _.has(memo, key) ? memo[key] : (memo[key] = func.apply(this, arguments));
613	    };
614	  };
615	
616	  // Delays a function for the given number of milliseconds, and then calls
617	  // it with the arguments supplied.
618	  _.delay = function(func, wait) {
619	    var args = slice.call(arguments, 2);
620	    return setTimeout(function(){ return func.apply(null, args); }, wait);
621	  };
622	
623	  // Defers a function, scheduling it to run after the current call stack has
624	  // cleared.
625	  _.defer = function(func) {
626	    return _.delay.apply(_, [func, 1].concat(slice.call(arguments, 1)));
627	  };
628	
629	  // Returns a function, that, when invoked, will only be triggered at most once
630	  // during a given window of time.
631	  _.throttle = function(func, wait) {
632	    var context, args, timeout, result;
633	    var previous = 0;
634	    var later = function() {
635	      previous = new Date;
636	      timeout = null;
637	      result = func.apply(context, args);
638	    };
639	    return function() {
640	      var now = new Date;
641	      var remaining = wait - (now - previous);
642	      context = this;
643	      args = arguments;
644	      if (remaining <= 0) {
645	        clearTimeout(timeout);
646	        timeout = null;
647	        previous = now;
648	        result = func.apply(context, args);
649	      } else if (!timeout) {
650	        timeout = setTimeout(later, remaining);
651	      }
652	      return result;
653	    };
654	  };
655	
656	  // Returns a function, that, as long as it continues to be invoked, will not
657	  // be triggered. The function will be called after it stops being called for
658	  // N milliseconds. If `immediate` is passed, trigger the function on the
659	  // leading edge, instead of the trailing.
660	  _.debounce = function(func, wait, immediate) {
661	    var timeout, result;
662	    return function() {
663	      var context = this, args = arguments;
664	      var later = function() {
665	        timeout = null;
666	        if (!immediate) result = func.apply(context, args);
667	      };
668	      var callNow = immediate && !timeout;
669	      clearTimeout(timeout);
670	      timeout = setTimeout(later, wait);
671	      if (callNow) result = func.apply(context, args);
672	      return result;
673	    };
674	  };
675	
676	  // Returns a function that will be executed at most one time, no matter how
677	  // often you call it. Useful for lazy initialization.
678	  _.once = function(func) {
679	    var ran = false, memo;
680	    return function() {
681	      if (ran) return memo;
682	      ran = true;
683	      memo = func.apply(this, arguments);
684	      func = null;
685	      return memo;
686	    };
687	  };
688	
689	  // Returns the first function passed as an argument to the second,
690	  // allowing you to adjust arguments, run code before and after, and
691	  // conditionally execute the original function.
692	  _.wrap = function(func, wrapper) {
693	    return function() {
694	      var args = [func];
695	      push.apply(args, arguments);
696	      return wrapper.apply(this, args);
697	    };
698	  };
699	
700	  // Returns a function that is the composition of a list of functions, each
701	  // consuming the return value of the function that follows.
702	  _.compose = function() {
703	    var funcs = arguments;
704	    return function() {
705	      var args = arguments;
706	      for (var i = funcs.length - 1; i >= 0; i--) {
707	        args = [funcs[i].apply(this, args)];
708	      }
709	      return args[0];
710	    };
711	  };
712	
713	  // Returns a function that will only be executed after being called N times.
714	  _.after = function(times, func) {
715	    if (times <= 0) return func();
716	    return function() {
717	      if (--times < 1) {
718	        return func.apply(this, arguments);
719	      }
720	    };
721	  };
722	
723	  // Object Functions
724	  // ----------------
725	
726	  // Retrieve the names of an object's properties.
727	  // Delegates to **ECMAScript 5**'s native `Object.keys`
728	  _.keys = nativeKeys || function(obj) {
729	    if (obj !== Object(obj)) throw new TypeError('Invalid object');
730	    var keys = [];
731	    for (var key in obj) if (_.has(obj, key)) keys[keys.length] = key;
732	    return keys;
733	  };
734	
735	  // Retrieve the values of an object's properties.
736	  _.values = function(obj) {
737	    var values = [];
738	    for (var key in obj) if (_.has(obj, key)) values.push(obj[key]);
739	    return values;
740	  };
741	
742	  // Convert an object into a list of `[key, value]` pairs.
743	  _.pairs = function(obj) {
744	    var pairs = [];
745	    for (var key in obj) if (_.has(obj, key)) pairs.push([key, obj[key]]);
746	    return pairs;
747	  };
748	
749	  // Invert the keys and values of an object. The values must be serializable.
750	  _.invert = function(obj) {
751	    var result = {};
752	    for (var key in obj) if (_.has(obj, key)) result[obj[key]] = key;
753	    return result;
754	  };
755	
756	  // Return a sorted list of the function names available on the object.
757	  // Aliased as `methods`
758	  _.functions = _.methods = function(obj) {
759	    var names = [];
760	    for (var key in obj) {
761	      if (_.isFunction(obj[key])) names.push(key);
762	    }
763	    return names.sort();
764	  };
765	
766	  // Extend a given object with all the properties in passed-in object(s).
767	  _.extend = function(obj) {
768	    each(slice.call(arguments, 1), function(source) {
769	      if (source) {
770	        for (var prop in source) {
771	          obj[prop] = source[prop];
772	        }
773	      }
774	    });
775	    return obj;
776	  };
777	
778	  // Return a copy of the object only containing the whitelisted properties.
779	  _.pick = function(obj) {
780	    var copy = {};
781	    var keys = concat.apply(ArrayProto, slice.call(arguments, 1));
782	    each(keys, function(key) {
783	      if (key in obj) copy[key] = obj[key];
784	    });
785	    return copy;
786	  };
787	
788	   // Return a copy of the object without the blacklisted properties.
789	  _.omit = function(obj) {
790	    var copy = {};
791	    var keys = concat.apply(ArrayProto, slice.call(arguments, 1));
792	    for (var key in obj) {
793	      if (!_.contains(keys, key)) copy[key] = obj[key];
794	    }
795	    return copy;
796	  };
797	
798	  // Fill in a given object with default properties.
799	  _.defaults = function(obj) {
800	    each(slice.call(arguments, 1), function(source) {
801	      if (source) {
802	        for (var prop in source) {
803	          if (obj[prop] == null) obj[prop] = source[prop];
804	        }
805	      }
806	    });
807	    return obj;
808	  };
809	
810	  // Create a (shallow-cloned) duplicate of an object.
811	  _.clone = function(obj) {
812	    if (!_.isObject(obj)) return obj;
813	    return _.isArray(obj) ? obj.slice() : _.extend({}, obj);
814	  };
815	
816	  // Invokes interceptor with the obj, and then returns obj.
817	  // The primary purpose of this method is to "tap into" a method chain, in
818	  // order to perform operations on intermediate results within the chain.
819	  _.tap = function(obj, interceptor) {
820	    interceptor(obj);
821	    return obj;
822	  };
823	
824	  // Internal recursive comparison function for `isEqual`.
825	  var eq = function(a, b, aStack, bStack) {
826	    // Identical objects are equal. `0 === -0`, but they aren't identical.
827	    // See the Harmony `egal` proposal: http://wiki.ecmascript.org/doku.php?id=harmony:egal.
828	    if (a === b) return a !== 0 || 1 / a == 1 / b;
829	    // A strict comparison is necessary because `null == undefined`.
830	    if (a == null || b == null) return a === b;
831	    // Unwrap any wrapped objects.
832	    if (a instanceof _) a = a._wrapped;
833	    if (b instanceof _) b = b._wrapped;
834	    // Compare `[[Class]]` names.
835	    var className = toString.call(a);
836	    if (className != toString.call(b)) return false;
837	    switch (className) {
838	      // Strings, numbers, dates, and booleans are compared by value.
839	      case '[object String]':
840	        // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
841	        // equivalent to `new String("5")`.
842	        return a == String(b);
843	      case '[object Number]':
844	        // `NaN`s are equivalent, but non-reflexive. An `egal` comparison is performed for
845	        // other numeric values.
846	        return a != +a ? b != +b : (a == 0 ? 1 / a == 1 / b : a == +b);
847	      case '[object Date]':
848	      case '[object Boolean]':
849	        // Coerce dates and booleans to numeric primitive values. Dates are compared by their
850	        // millisecond representations. Note that invalid dates with millisecond representations
851	        // of `NaN` are not equivalent.
852	        return +a == +b;
853	      // RegExps are compared by their source patterns and flags.
854	      case '[object RegExp]':
855	        return a.source == b.source &&
856	               a.global == b.global &&
857	               a.multiline == b.multiline &&
858	               a.ignoreCase == b.ignoreCase;
859	    }
860	    if (typeof a != 'object' || typeof b != 'object') return false;
861	    // Assume equality for cyclic structures. The algorithm for detecting cyclic
862	    // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
863	    var length = aStack.length;
864	    while (length--) {
865	      // Linear search. Performance is inversely proportional to the number of
866	      // unique nested structures.
867	      if (aStack[length] == a) return bStack[length] == b;
868	    }
869	    // Add the first object to the stack of traversed objects.
870	    aStack.push(a);
871	    bStack.push(b);
872	    var size = 0, result = true;
873	    // Recursively compare objects and arrays.
874	    if (className == '[object Array]') {
875	      // Compare array lengths to determine if a deep comparison is necessary.
876	      size = a.length;
877	      result = size == b.length;
878	      if (result) {
879	        // Deep compare the contents, ignoring non-numeric properties.
880	        while (size--) {
881	          if (!(result = eq(a[size], b[size], aStack, bStack))) break;
882	        }
883	      }
884	    } else {
885	      // Objects with different constructors are not equivalent, but `Object`s
886	      // from different frames are.
887	      var aCtor = a.constructor, bCtor = b.constructor;
888	      if (aCtor !== bCtor && !(_.isFunction(aCtor) && (aCtor instanceof aCtor) &&
889	                               _.isFunction(bCtor) && (bCtor instanceof bCtor))) {
890	        return false;
891	      }
892	      // Deep compare objects.
893	      for (var key in a) {
894	        if (_.has(a, key)) {
895	          // Count the expected number of properties.
896	          size++;
897	          // Deep compare each member.
898	          if (!(result = _.has(b, key) && eq(a[key], b[key], aStack, bStack))) break;
899	        }
900	      }
901	      // Ensure that both objects contain the same number of properties.
902	      if (result) {
903	        for (key in b) {
904	          if (_.has(b, key) && !(size--)) break;
905	        }
906	        result = !size;
907	      }
908	    }
909	    // Remove the first object from the stack of traversed objects.
910	    aStack.pop();
911	    bStack.pop();
912	    return result;
913	  };
914	
915	  // Perform a deep comparison to check if two objects are equal.
916	  _.isEqual = function(a, b) {
917	    return eq(a, b, [], []);
918	  };
919	
920	  // Is a given array, string, or object empty?
921	  // An "empty" object has no enumerable own-properties.
922	  _.isEmpty = function(obj) {
923	    if (obj == null) return true;
924	    if (_.isArray(obj) || _.isString(obj)) return obj.length === 0;
925	    for (var key in obj) if (_.has(obj, key)) return false;
926	    return true;
927	  };
928	
929	  // Is a given value a DOM element?
930	  _.isElement = function(obj) {
931	    return !!(obj && obj.nodeType === 1);
932	  };
933	
934	  // Is a given value an array?
935	  // Delegates to ECMA5's native Array.isArray
936	  _.isArray = nativeIsArray || function(obj) {
937	    return toString.call(obj) == '[object Array]';
938	  };
939	
940	  // Is a given variable an object?
941	  _.isObject = function(obj) {
942	    return obj === Object(obj);
943	  };
944	
945	  // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp.
946	  each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp'], function(name) {
947	    _['is' + name] = function(obj) {
948	      return toString.call(obj) == '[object ' + name + ']';
949	    };
950	  });
951	
952	  // Define a fallback version of the method in browsers (ahem, IE), where
953	  // there isn't any inspectable "Arguments" type.
954	  if (!_.isArguments(arguments)) {
955	    _.isArguments = function(obj) {
956	      return !!(obj && _.has(obj, 'callee'));
957	    };
958	  }
959	
960	  // Optimize `isFunction` if appropriate.
961	  if (typeof (/./) !== 'function') {
962	    _.isFunction = function(obj) {
963	      return typeof obj === 'function';
964	    };
965	  }
966	
967	  // Is a given object a finite number?
968	  _.isFinite = function(obj) {
969	    return isFinite(obj) && !isNaN(parseFloat(obj));
970	  };
971	
972	  // Is the given value `NaN`? (NaN is the only number which does not equal itself).
973	  _.isNaN = function(obj) {
974	    return _.isNumber(obj) && obj != +obj;
975	  };
976	
977	  // Is a given value a boolean?
978	  _.isBoolean = function(obj) {
979	    return obj === true || obj === false || toString.call(obj) == '[object Boolean]';
980	  };
981	
982	  // Is a given value equal to null?
983	  _.isNull = function(obj) {
984	    return obj === null;
985	  };
986	
987	  // Is a given variable undefined?
988	  _.isUndefined = function(obj) {
989	    return obj === void 0;
990	  };
991	
992	  // Shortcut function for checking if an object has a given property directly
993	  // on itself (in other words, not on a prototype).
994	  _.has = function(obj, key) {
995	    return hasOwnProperty.call(obj, key);
996	  };
997	
998	  // Utility Functions
999	  // -----------------
1000	
1001	  // Run Underscore.js in *noConflict* mode, returning the `_` variable to its
1002	  // previous owner. Returns a reference to the Underscore object.
1003	  _.noConflict = function() {
1004	    root._ = previousUnderscore;
1005	    return this;
1006	  };
1007	
1008	  // Keep the identity function around for default iterators.
1009	  _.identity = function(value) {
1010	    return value;
1011	  };
1012	
1013	  // Run a function **n** times.
1014	  _.times = function(n, iterator, context) {
1015	    var accum = Array(n);
1016	    for (var i = 0; i < n; i++) accum[i] = iterator.call(context, i);
1017	    return accum;
1018	  };
1019	
1020	  // Return a random integer between min and max (inclusive).
1021	  _.random = function(min, max) {
1022	    if (max == null) {
1023	      max = min;
1024	      min = 0;
1025	    }
1026	    return min + Math.floor(Math.random() * (max - min + 1));
1027	  };
1028	
1029	  // List of HTML entities for escaping.
1030	  var entityMap = {
1031	    escape: {
1032	      '&': '&amp;',
1033	      '<': '&lt;',
1034	      '>': '&gt;',
1035	      '"': '&quot;',
1036	      "'": '&#x27;',
1037	      '/': '&#x2F;'
1038	    }
1039	  };
1040	  entityMap.unescape = _.invert(entityMap.escape);
1041	
1042	  // Regexes containing the keys and values listed immediately above.
1043	  var entityRegexes = {
1044	    escape:   new RegExp('[' + _.keys(entityMap.escape).join('') + ']', 'g'),
1045	    unescape: new RegExp('(' + _.keys(entityMap.unescape).join('|') + ')', 'g')
1046	  };
1047	
1048	  // Functions for escaping and unescaping strings to/from HTML interpolation.
1049	  _.each(['escape', 'unescape'], function(method) {
1050	    _[method] = function(string) {
1051	      if (string == null) return '';
1052	      return ('' + string).replace(entityRegexes[method], function(match) {
1053	        return entityMap[method][match];
1054	      });
1055	    };
1056	  });
1057	
1058	  // If the value of the named property is a function then invoke it;
1059	  // otherwise, return it.
1060	  _.result = function(object, property) {
1061	    if (object == null) return null;
1062	    var value = object[property];
1063	    return _.isFunction(value) ? value.call(object) : value;
1064	  };
1065	
1066	  // Add your own custom functions to the Underscore object.
1067	  _.mixin = function(obj) {
1068	    each(_.functions(obj), function(name){
1069	      var func = _[name] = obj[name];
1070	      _.prototype[name] = function() {
1071	        var args = [this._wrapped];
1072	        push.apply(args, arguments);
1073	        return result.call(this, func.apply(_, args));
1074	      };
1075	    });
1076	  };
1077	
1078	  // Generate a unique integer id (unique within the entire client session).
1079	  // Useful for temporary DOM ids.
1080	  var idCounter = 0;
1081	  _.uniqueId = function(prefix) {
1082	    var id = ++idCounter + '';
1083	    return prefix ? prefix + id : id;
1084	  };
1085	
1086	  // By default, Underscore uses ERB-style template delimiters, change the
1087	  // following template settings to use alternative delimiters.
1088	  _.templateSettings = {
1089	    evaluate    : /<%([\s\S]+?)%>/g,
1090	    interpolate : /<%=([\s\S]+?)%>/g,
1091	    escape      : /<%-([\s\S]+?)%>/g
1092	  };
1093	
1094	  // When customizing `templateSettings`, if you don't want to define an
1095	  // interpolation, evaluation or escaping regex, we need one that is
1096	  // guaranteed not to match.
1097	  var noMatch = /(.)^/;
1098	
1099	  // Certain characters need to be escaped so that they can be put into a
1100	  // string literal.
1101	  var escapes = {
1102	    "'":      "'",
1103	    '\\':     '\\',
1104	    '\r':     'r',
1105	    '\n':     'n',
1106	    '\t':     't',
1107	    '\u2028': 'u2028',
1108	    '\u2029': 'u2029'
1109	  };
1110	
1111	  var escaper = /\\|'|\r|\n|\t|\u2028|\u2029/g;
1112	
1113	  // JavaScript micro-templating, similar to John Resig's implementation.
1114	  // Underscore templating handles arbitrary delimiters, preserves whitespace,
1115	  // and correctly escapes quotes within interpolated code.
1116	  _.template = function(text, data, settings) {
1117	    var render;
1118	    settings = _.defaults({}, settings, _.templateSettings);
1119	
1120	    // Combine delimiters into one regular expression via alternation.
1121	    var matcher = new RegExp([
1122	      (settings.escape || noMatch).source,
1123	      (settings.interpolate || noMatch).source,
1124	      (settings.evaluate || noMatch).source
1125	    ].join('|') + '|$', 'g');
1126	
1127	    // Compile the template source, escaping string literals appropriately.
1128	    var index = 0;
1129	    var source = "__p+='";
1130	    text.replace(matcher, function(match, escape, interpolate, evaluate, offset) {
1131	      source += text.slice(index, offset)
1132	        .replace(escaper, function(match) { return '\\' + escapes[match]; });
1133	
1134	      if (escape) {
1135	        source += "'+\n((__t=(" + escape + "))==null?'':_.escape(__t))+\n'";
1136	      }
1137	      if (interpolate) {
1138	        source += "'+\n((__t=(" + interpolate + "))==null?'':__t)+\n'";
1139	      }
1140	      if (evaluate) {
1141	        source += "';\n" + evaluate + "\n__p+='";
1142	      }
1143	      index = offset + match.length;
1144	      return match;
1145	    });
1146	    source += "';\n";
1147	
1148	    // If a variable is not specified, place data values in local scope.
1149	    if (!settings.variable) source = 'with(obj||{}){\n' + source + '}\n';
1150	
1151	    source = "var __t,__p='',__j=Array.prototype.join," +
1152	      "print=function(){__p+=__j.call(arguments,'');};\n" +
1153	      source + "return __p;\n";
1154	
1155	    try {
1156	      render = new Function(settings.variable || 'obj', '_', source);
1157	    } catch (e) {
1158	      e.source = source;
1159	      throw e;
1160	    }
1161	
1162	    if (data) return render(data, _);
1163	    var template = function(data) {
1164	      return render.call(this, data, _);
1165	    };
1166	
1167	    // Provide the compiled function source as a convenience for precompilation.
1168	    template.source = 'function(' + (settings.variable || 'obj') + '){\n' + source + '}';
1169	
1170	    return template;
1171	  };
1172	
1173	  // Add a "chain" function, which will delegate to the wrapper.
1174	  _.chain = function(obj) {
1175	    return _(obj).chain();
1176	  };
1177	
1178	  // OOP
1179	  // ---------------
1180	  // If Underscore is called as a function, it returns a wrapped object that
1181	  // can be used OO-style. This wrapper holds altered versions of all the
1182	  // underscore functions. Wrapped objects may be chained.
1183	
1184	  // Helper function to continue chaining intermediate results.
1185	  var result = function(obj) {
1186	    return this._chain ? _(obj).chain() : obj;
1187	  };
1188	
1189	  // Add all of the Underscore functions to the wrapper object.
1190	  _.mixin(_);
1191	
1192	  // Add all mutator Array functions to the wrapper.
1193	  each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
1194	    var method = ArrayProto[name];
1195	    _.prototype[name] = function() {
1196	      var obj = this._wrapped;
1197	      method.apply(obj, arguments);
1198	      if ((name == 'shift' || name == 'splice') && obj.length === 0) delete obj[0];
1199	      return result.call(this, obj);
1200	    };
1201	  });
1202	
1203	  // Add all accessor Array functions to the wrapper.
1204	  each(['concat', 'join', 'slice'], function(name) {
1205	    var method = ArrayProto[name];
1206	    _.prototype[name] = function() {
1207	      return result.call(this, method.apply(this._wrapped, arguments));
1208	    };
1209	  });
1210	
1211	  _.extend(_.prototype, {
1212	
1213	    // Start chaining a wrapped Underscore object.
1214	    chain: function() {
1215	      this._chain = true;
1216	      return this;
1217	    },
1218	
1219	    // Extracts the result from a wrapped and chained object.
1220	    value: function() {
1221	      return this._wrapped;
1222	    }
1223	
1224	  });
1225	
1226	}).call(this);