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/app/node_modules/backbone/test/vendor/underscore-1.3.1.js

https://bitbucket.org/jorritposthuma/inventory-counter-mobile
JavaScript | 999 lines | 711 code | 94 blank | 194 comment | 221 complexity | 4eb64db36175fefa3e36b9e57606512c MD5 | raw file
Possible License(s): MIT, Apache-2.0
  1//     Underscore.js 1.3.1
  2//     (c) 2009-2012 Jeremy Ashkenas, DocumentCloud Inc.
  3//     Underscore is freely distributable under the MIT license.
  4//     Portions of Underscore are inspired or borrowed from Prototype,
  5//     Oliver Steele's Functional, and John Resig's Micro-Templating.
  6//     For all details and documentation:
  7//     http://documentcloud.github.com/underscore
  8
  9(function() {
 10
 11  // Baseline setup
 12  // --------------
 13
 14  // Establish the root object, `window` in the browser, or `global` on the server.
 15  var root = this;
 16
 17  // Save the previous value of the `_` variable.
 18  var previousUnderscore = root._;
 19
 20  // Establish the object that gets returned to break out of a loop iteration.
 21  var breaker = {};
 22
 23  // Save bytes in the minified (but not gzipped) version:
 24  var ArrayProto = Array.prototype, ObjProto = Object.prototype, FuncProto = Function.prototype;
 25
 26  // Create quick reference variables for speed access to core prototypes.
 27  var slice            = ArrayProto.slice,
 28      unshift          = ArrayProto.unshift,
 29      toString         = ObjProto.toString,
 30      hasOwnProperty   = ObjProto.hasOwnProperty;
 31
 32  // All **ECMAScript 5** native function implementations that we hope to use
 33  // are declared here.
 34  var
 35    nativeForEach      = ArrayProto.forEach,
 36    nativeMap          = ArrayProto.map,
 37    nativeReduce       = ArrayProto.reduce,
 38    nativeReduceRight  = ArrayProto.reduceRight,
 39    nativeFilter       = ArrayProto.filter,
 40    nativeEvery        = ArrayProto.every,
 41    nativeSome         = ArrayProto.some,
 42    nativeIndexOf      = ArrayProto.indexOf,
 43    nativeLastIndexOf  = ArrayProto.lastIndexOf,
 44    nativeIsArray      = Array.isArray,
 45    nativeKeys         = Object.keys,
 46    nativeBind         = FuncProto.bind;
 47
 48  // Create a safe reference to the Underscore object for use below.
 49  var _ = function(obj) { return new wrapper(obj); };
 50
 51  // Export the Underscore object for **Node.js**, with
 52  // backwards-compatibility for the old `require()` API. If we're in
 53  // the browser, add `_` as a global object via a string identifier,
 54  // for Closure Compiler "advanced" mode.
 55  if (typeof exports !== 'undefined') {
 56    if (typeof module !== 'undefined' && module.exports) {
 57      exports = module.exports = _;
 58    }
 59    exports._ = _;
 60  } else {
 61    root['_'] = _;
 62  }
 63
 64  // Current version.
 65  _.VERSION = '1.3.1';
 66
 67  // Collection Functions
 68  // --------------------
 69
 70  // The cornerstone, an `each` implementation, aka `forEach`.
 71  // Handles objects with the built-in `forEach`, arrays, and raw objects.
 72  // Delegates to **ECMAScript 5**'s native `forEach` if available.
 73  var each = _.each = _.forEach = function(obj, iterator, context) {
 74    if (obj == null) return;
 75    if (nativeForEach && obj.forEach === nativeForEach) {
 76      obj.forEach(iterator, context);
 77    } else if (obj.length === +obj.length) {
 78      for (var i = 0, l = obj.length; i < l; i++) {
 79        if (i in obj && iterator.call(context, obj[i], i, obj) === breaker) return;
 80      }
 81    } else {
 82      for (var key in obj) {
 83        if (_.has(obj, key)) {
 84          if (iterator.call(context, obj[key], key, obj) === breaker) return;
 85        }
 86      }
 87    }
 88  };
 89
 90  // Return the results of applying the iterator to each element.
 91  // Delegates to **ECMAScript 5**'s native `map` if available.
 92  _.map = _.collect = function(obj, iterator, context) {
 93    var results = [];
 94    if (obj == null) return results;
 95    if (nativeMap && obj.map === nativeMap) return obj.map(iterator, context);
 96    each(obj, function(value, index, list) {
 97      results[results.length] = iterator.call(context, value, index, list);
 98    });
 99    if (obj.length === +obj.length) results.length = obj.length;
100    return results;
101  };
102
103  // **Reduce** builds up a single result from a list of values, aka `inject`,
104  // or `foldl`. Delegates to **ECMAScript 5**'s native `reduce` if available.
105  _.reduce = _.foldl = _.inject = function(obj, iterator, memo, context) {
106    var initial = arguments.length > 2;
107    if (obj == null) obj = [];
108    if (nativeReduce && obj.reduce === nativeReduce) {
109      if (context) iterator = _.bind(iterator, context);
110      return initial ? obj.reduce(iterator, memo) : obj.reduce(iterator);
111    }
112    each(obj, function(value, index, list) {
113      if (!initial) {
114        memo = value;
115        initial = true;
116      } else {
117        memo = iterator.call(context, memo, value, index, list);
118      }
119    });
120    if (!initial) throw new TypeError('Reduce of empty array with no initial value');
121    return memo;
122  };
123
124  // The right-associative version of reduce, also known as `foldr`.
125  // Delegates to **ECMAScript 5**'s native `reduceRight` if available.
126  _.reduceRight = _.foldr = function(obj, iterator, memo, context) {
127    var initial = arguments.length > 2;
128    if (obj == null) obj = [];
129    if (nativeReduceRight && obj.reduceRight === nativeReduceRight) {
130      if (context) iterator = _.bind(iterator, context);
131      return initial ? obj.reduceRight(iterator, memo) : obj.reduceRight(iterator);
132    }
133    var reversed = _.toArray(obj).reverse();
134    if (context && !initial) iterator = _.bind(iterator, context);
135    return initial ? _.reduce(reversed, iterator, memo, context) : _.reduce(reversed, iterator);
136  };
137
138  // Return the first value which passes a truth test. Aliased as `detect`.
139  _.find = _.detect = function(obj, iterator, context) {
140    var result;
141    any(obj, function(value, index, list) {
142      if (iterator.call(context, value, index, list)) {
143        result = value;
144        return true;
145      }
146    });
147    return result;
148  };
149
150  // Return all the elements that pass a truth test.
151  // Delegates to **ECMAScript 5**'s native `filter` if available.
152  // Aliased as `select`.
153  _.filter = _.select = function(obj, iterator, context) {
154    var results = [];
155    if (obj == null) return results;
156    if (nativeFilter && obj.filter === nativeFilter) return obj.filter(iterator, context);
157    each(obj, function(value, index, list) {
158      if (iterator.call(context, value, index, list)) results[results.length] = value;
159    });
160    return results;
161  };
162
163  // Return all the elements for which a truth test fails.
164  _.reject = function(obj, iterator, context) {
165    var results = [];
166    if (obj == null) return results;
167    each(obj, function(value, index, list) {
168      if (!iterator.call(context, value, index, list)) results[results.length] = value;
169    });
170    return results;
171  };
172
173  // Determine whether all of the elements match a truth test.
174  // Delegates to **ECMAScript 5**'s native `every` if available.
175  // Aliased as `all`.
176  _.every = _.all = function(obj, iterator, context) {
177    var result = true;
178    if (obj == null) return result;
179    if (nativeEvery && obj.every === nativeEvery) return obj.every(iterator, context);
180    each(obj, function(value, index, list) {
181      if (!(result = result && iterator.call(context, value, index, list))) return breaker;
182    });
183    return result;
184  };
185
186  // Determine if at least one element in the object matches a truth test.
187  // Delegates to **ECMAScript 5**'s native `some` if available.
188  // Aliased as `any`.
189  var any = _.some = _.any = function(obj, iterator, context) {
190    iterator || (iterator = _.identity);
191    var result = false;
192    if (obj == null) return result;
193    if (nativeSome && obj.some === nativeSome) return obj.some(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 a given value is included in the array or object using `===`.
201  // Aliased as `contains`.
202  _.include = _.contains = function(obj, target) {
203    var found = false;
204    if (obj == null) return found;
205    if (nativeIndexOf && obj.indexOf === nativeIndexOf) return obj.indexOf(target) != -1;
206    found = any(obj, function(value) {
207      return value === target;
208    });
209    return found;
210  };
211
212  // Invoke a method (with arguments) on every item in a collection.
213  _.invoke = function(obj, method) {
214    var args = slice.call(arguments, 2);
215    return _.map(obj, function(value) {
216      return (_.isFunction(method) ? method || value : value[method]).apply(value, args);
217    });
218  };
219
220  // Convenience version of a common use case of `map`: fetching a property.
221  _.pluck = function(obj, key) {
222    return _.map(obj, function(value){ return value[key]; });
223  };
224
225  // Return the maximum element or (element-based computation).
226  _.max = function(obj, iterator, context) {
227    if (!iterator && _.isArray(obj)) return Math.max.apply(Math, obj);
228    if (!iterator && _.isEmpty(obj)) return -Infinity;
229    var result = {computed : -Infinity};
230    each(obj, function(value, index, list) {
231      var computed = iterator ? iterator.call(context, value, index, list) : value;
232      computed >= result.computed && (result = {value : value, computed : computed});
233    });
234    return result.value;
235  };
236
237  // Return the minimum element (or element-based computation).
238  _.min = function(obj, iterator, context) {
239    if (!iterator && _.isArray(obj)) return Math.min.apply(Math, obj);
240    if (!iterator && _.isEmpty(obj)) return Infinity;
241    var result = {computed : Infinity};
242    each(obj, function(value, index, list) {
243      var computed = iterator ? iterator.call(context, value, index, list) : value;
244      computed < result.computed && (result = {value : value, computed : computed});
245    });
246    return result.value;
247  };
248
249  // Shuffle an array.
250  _.shuffle = function(obj) {
251    var shuffled = [], rand;
252    each(obj, function(value, index, list) {
253      if (index == 0) {
254        shuffled[0] = value;
255      } else {
256        rand = Math.floor(Math.random() * (index + 1));
257        shuffled[index] = shuffled[rand];
258        shuffled[rand] = value;
259      }
260    });
261    return shuffled;
262  };
263
264  // Sort the object's values by a criterion produced by an iterator.
265  _.sortBy = function(obj, iterator, context) {
266    return _.pluck(_.map(obj, function(value, index, list) {
267      return {
268        value : value,
269        criteria : iterator.call(context, value, index, list)
270      };
271    }).sort(function(left, right) {
272      var a = left.criteria, b = right.criteria;
273      return a < b ? -1 : a > b ? 1 : 0;
274    }), 'value');
275  };
276
277  // Groups the object's values by a criterion. Pass either a string attribute
278  // to group by, or a function that returns the criterion.
279  _.groupBy = function(obj, val) {
280    var result = {};
281    var iterator = _.isFunction(val) ? val : function(obj) { return obj[val]; };
282    each(obj, function(value, index) {
283      var key = iterator(value, index);
284      (result[key] || (result[key] = [])).push(value);
285    });
286    return result;
287  };
288
289  // Use a comparator function to figure out at what index an object should
290  // be inserted so as to maintain order. Uses binary search.
291  _.sortedIndex = function(array, obj, iterator) {
292    iterator || (iterator = _.identity);
293    var low = 0, high = array.length;
294    while (low < high) {
295      var mid = (low + high) >> 1;
296      iterator(array[mid]) < iterator(obj) ? low = mid + 1 : high = mid;
297    }
298    return low;
299  };
300
301  // Safely convert anything iterable into a real, live array.
302  _.toArray = function(iterable) {
303    if (!iterable)                return [];
304    if (iterable.toArray)         return iterable.toArray();
305    if (_.isArray(iterable))      return slice.call(iterable);
306    if (_.isArguments(iterable))  return slice.call(iterable);
307    return _.values(iterable);
308  };
309
310  // Return the number of elements in an object.
311  _.size = function(obj) {
312    return _.toArray(obj).length;
313  };
314
315  // Array Functions
316  // ---------------
317
318  // Get the first element of an array. Passing **n** will return the first N
319  // values in the array. Aliased as `head`. The **guard** check allows it to work
320  // with `_.map`.
321  _.first = _.head = function(array, n, guard) {
322    return (n != null) && !guard ? slice.call(array, 0, n) : array[0];
323  };
324
325  // Returns everything but the last entry of the array. Especcialy useful on
326  // the arguments object. Passing **n** will return all the values in
327  // the array, excluding the last N. The **guard** check allows it to work with
328  // `_.map`.
329  _.initial = function(array, n, guard) {
330    return slice.call(array, 0, array.length - ((n == null) || guard ? 1 : n));
331  };
332
333  // Get the last element of an array. Passing **n** will return the last N
334  // values in the array. The **guard** check allows it to work with `_.map`.
335  _.last = function(array, n, guard) {
336    if ((n != null) && !guard) {
337      return slice.call(array, Math.max(array.length - n, 0));
338    } else {
339      return array[array.length - 1];
340    }
341  };
342
343  // Returns everything but the first entry of the array. Aliased as `tail`.
344  // Especially useful on the arguments object. Passing an **index** will return
345  // the rest of the values in the array from that index onward. The **guard**
346  // check allows it to work with `_.map`.
347  _.rest = _.tail = function(array, index, guard) {
348    return slice.call(array, (index == null) || guard ? 1 : index);
349  };
350
351  // Trim out all falsy values from an array.
352  _.compact = function(array) {
353    return _.filter(array, function(value){ return !!value; });
354  };
355
356  // Return a completely flattened version of an array.
357  _.flatten = function(array, shallow) {
358    return _.reduce(array, function(memo, value) {
359      if (_.isArray(value)) return memo.concat(shallow ? value : _.flatten(value));
360      memo[memo.length] = value;
361      return memo;
362    }, []);
363  };
364
365  // Return a version of the array that does not contain the specified value(s).
366  _.without = function(array) {
367    return _.difference(array, slice.call(arguments, 1));
368  };
369
370  // Produce a duplicate-free version of the array. If the array has already
371  // been sorted, you have the option of using a faster algorithm.
372  // Aliased as `unique`.
373  _.uniq = _.unique = function(array, isSorted, iterator) {
374    var initial = iterator ? _.map(array, iterator) : array;
375    var result = [];
376    _.reduce(initial, function(memo, el, i) {
377      if (0 == i || (isSorted === true ? _.last(memo) != el : !_.include(memo, el))) {
378        memo[memo.length] = el;
379        result[result.length] = array[i];
380      }
381      return memo;
382    }, []);
383    return result;
384  };
385
386  // Produce an array that contains the union: each distinct element from all of
387  // the passed-in arrays.
388  _.union = function() {
389    return _.uniq(_.flatten(arguments, true));
390  };
391
392  // Produce an array that contains every item shared between all the
393  // passed-in arrays. (Aliased as "intersect" for back-compat.)
394  _.intersection = _.intersect = function(array) {
395    var rest = slice.call(arguments, 1);
396    return _.filter(_.uniq(array), function(item) {
397      return _.every(rest, function(other) {
398        return _.indexOf(other, item) >= 0;
399      });
400    });
401  };
402
403  // Take the difference between one array and a number of other arrays.
404  // Only the elements present in just the first array will remain.
405  _.difference = function(array) {
406    var rest = _.flatten(slice.call(arguments, 1));
407    return _.filter(array, function(value){ return !_.include(rest, value); });
408  };
409
410  // Zip together multiple lists into a single array -- elements that share
411  // an index go together.
412  _.zip = function() {
413    var args = slice.call(arguments);
414    var length = _.max(_.pluck(args, 'length'));
415    var results = new Array(length);
416    for (var i = 0; i < length; i++) results[i] = _.pluck(args, "" + i);
417    return results;
418  };
419
420  // If the browser doesn't supply us with indexOf (I'm looking at you, **MSIE**),
421  // we need this function. Return the position of the first occurrence of an
422  // item in an array, or -1 if the item is not included in the array.
423  // Delegates to **ECMAScript 5**'s native `indexOf` if available.
424  // If the array is large and already in sort order, pass `true`
425  // for **isSorted** to use binary search.
426  _.indexOf = function(array, item, isSorted) {
427    if (array == null) return -1;
428    var i, l;
429    if (isSorted) {
430      i = _.sortedIndex(array, item);
431      return array[i] === item ? i : -1;
432    }
433    if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item);
434    for (i = 0, l = array.length; i < l; i++) if (i in array && array[i] === item) return i;
435    return -1;
436  };
437
438  // Delegates to **ECMAScript 5**'s native `lastIndexOf` if available.
439  _.lastIndexOf = function(array, item) {
440    if (array == null) return -1;
441    if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) return array.lastIndexOf(item);
442    var i = array.length;
443    while (i--) if (i in array && array[i] === item) return i;
444    return -1;
445  };
446
447  // Generate an integer Array containing an arithmetic progression. A port of
448  // the native Python `range()` function. See
449  // [the Python documentation](http://docs.python.org/library/functions.html#range).
450  _.range = function(start, stop, step) {
451    if (arguments.length <= 1) {
452      stop = start || 0;
453      start = 0;
454    }
455    step = arguments[2] || 1;
456
457    var len = Math.max(Math.ceil((stop - start) / step), 0);
458    var idx = 0;
459    var range = new Array(len);
460
461    while(idx < len) {
462      range[idx++] = start;
463      start += step;
464    }
465
466    return range;
467  };
468
469  // Function (ahem) Functions
470  // ------------------
471
472  // Reusable constructor function for prototype setting.
473  var ctor = function(){};
474
475  // Create a function bound to a given object (assigning `this`, and arguments,
476  // optionally). Binding with arguments is also known as `curry`.
477  // Delegates to **ECMAScript 5**'s native `Function.bind` if available.
478  // We check for `func.bind` first, to fail fast when `func` is undefined.
479  _.bind = function bind(func, context) {
480    var bound, args;
481    if (func.bind === nativeBind && nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
482    if (!_.isFunction(func)) throw new TypeError;
483    args = slice.call(arguments, 2);
484    return bound = function() {
485      if (!(this instanceof bound)) return func.apply(context, args.concat(slice.call(arguments)));
486      ctor.prototype = func.prototype;
487      var self = new ctor;
488      var result = func.apply(self, args.concat(slice.call(arguments)));
489      if (Object(result) === result) return result;
490      return self;
491    };
492  };
493
494  // Bind all of an object's methods to that object. Useful for ensuring that
495  // all callbacks defined on an object belong to it.
496  _.bindAll = function(obj) {
497    var funcs = slice.call(arguments, 1);
498    if (funcs.length == 0) funcs = _.functions(obj);
499    each(funcs, function(f) { obj[f] = _.bind(obj[f], obj); });
500    return obj;
501  };
502
503  // Memoize an expensive function by storing its results.
504  _.memoize = function(func, hasher) {
505    var memo = {};
506    hasher || (hasher = _.identity);
507    return function() {
508      var key = hasher.apply(this, arguments);
509      return _.has(memo, key) ? memo[key] : (memo[key] = func.apply(this, arguments));
510    };
511  };
512
513  // Delays a function for the given number of milliseconds, and then calls
514  // it with the arguments supplied.
515  _.delay = function(func, wait) {
516    var args = slice.call(arguments, 2);
517    return setTimeout(function(){ return func.apply(func, args); }, wait);
518  };
519
520  // Defers a function, scheduling it to run after the current call stack has
521  // cleared.
522  _.defer = function(func) {
523    return _.delay.apply(_, [func, 1].concat(slice.call(arguments, 1)));
524  };
525
526  // Returns a function, that, when invoked, will only be triggered at most once
527  // during a given window of time.
528  _.throttle = function(func, wait) {
529    var context, args, timeout, throttling, more;
530    var whenDone = _.debounce(function(){ more = throttling = false; }, wait);
531    return function() {
532      context = this; args = arguments;
533      var later = function() {
534        timeout = null;
535        if (more) func.apply(context, args);
536        whenDone();
537      };
538      if (!timeout) timeout = setTimeout(later, wait);
539      if (throttling) {
540        more = true;
541      } else {
542        func.apply(context, args);
543      }
544      whenDone();
545      throttling = true;
546    };
547  };
548
549  // Returns a function, that, as long as it continues to be invoked, will not
550  // be triggered. The function will be called after it stops being called for
551  // N milliseconds.
552  _.debounce = function(func, wait) {
553    var timeout;
554    return function() {
555      var context = this, args = arguments;
556      var later = function() {
557        timeout = null;
558        func.apply(context, args);
559      };
560      clearTimeout(timeout);
561      timeout = setTimeout(later, wait);
562    };
563  };
564
565  // Returns a function that will be executed at most one time, no matter how
566  // often you call it. Useful for lazy initialization.
567  _.once = function(func) {
568    var ran = false, memo;
569    return function() {
570      if (ran) return memo;
571      ran = true;
572      return memo = func.apply(this, arguments);
573    };
574  };
575
576  // Returns the first function passed as an argument to the second,
577  // allowing you to adjust arguments, run code before and after, and
578  // conditionally execute the original function.
579  _.wrap = function(func, wrapper) {
580    return function() {
581      var args = [func].concat(slice.call(arguments, 0));
582      return wrapper.apply(this, args);
583    };
584  };
585
586  // Returns a function that is the composition of a list of functions, each
587  // consuming the return value of the function that follows.
588  _.compose = function() {
589    var funcs = arguments;
590    return function() {
591      var args = arguments;
592      for (var i = funcs.length - 1; i >= 0; i--) {
593        args = [funcs[i].apply(this, args)];
594      }
595      return args[0];
596    };
597  };
598
599  // Returns a function that will only be executed after being called N times.
600  _.after = function(times, func) {
601    if (times <= 0) return func();
602    return function() {
603      if (--times < 1) { return func.apply(this, arguments); }
604    };
605  };
606
607  // Object Functions
608  // ----------------
609
610  // Retrieve the names of an object's properties.
611  // Delegates to **ECMAScript 5**'s native `Object.keys`
612  _.keys = nativeKeys || function(obj) {
613    if (obj !== Object(obj)) throw new TypeError('Invalid object');
614    var keys = [];
615    for (var key in obj) if (_.has(obj, key)) keys[keys.length] = key;
616    return keys;
617  };
618
619  // Retrieve the values of an object's properties.
620  _.values = function(obj) {
621    return _.map(obj, _.identity);
622  };
623
624  // Return a sorted list of the function names available on the object.
625  // Aliased as `methods`
626  _.functions = _.methods = function(obj) {
627    var names = [];
628    for (var key in obj) {
629      if (_.isFunction(obj[key])) names.push(key);
630    }
631    return names.sort();
632  };
633
634  // Extend a given object with all the properties in passed-in object(s).
635  _.extend = function(obj) {
636    each(slice.call(arguments, 1), function(source) {
637      for (var prop in source) {
638        obj[prop] = source[prop];
639      }
640    });
641    return obj;
642  };
643
644  // Fill in a given object with default properties.
645  _.defaults = function(obj) {
646    each(slice.call(arguments, 1), function(source) {
647      for (var prop in source) {
648        if (obj[prop] == null) obj[prop] = source[prop];
649      }
650    });
651    return obj;
652  };
653
654  // Create a (shallow-cloned) duplicate of an object.
655  _.clone = function(obj) {
656    if (!_.isObject(obj)) return obj;
657    return _.isArray(obj) ? obj.slice() : _.extend({}, obj);
658  };
659
660  // Invokes interceptor with the obj, and then returns obj.
661  // The primary purpose of this method is to "tap into" a method chain, in
662  // order to perform operations on intermediate results within the chain.
663  _.tap = function(obj, interceptor) {
664    interceptor(obj);
665    return obj;
666  };
667
668  // Internal recursive comparison function.
669  function eq(a, b, stack) {
670    // Identical objects are equal. `0 === -0`, but they aren't identical.
671    // See the Harmony `egal` proposal: http://wiki.ecmascript.org/doku.php?id=harmony:egal.
672    if (a === b) return a !== 0 || 1 / a == 1 / b;
673    // A strict comparison is necessary because `null == undefined`.
674    if (a == null || b == null) return a === b;
675    // Unwrap any wrapped objects.
676    if (a._chain) a = a._wrapped;
677    if (b._chain) b = b._wrapped;
678    // Invoke a custom `isEqual` method if one is provided.
679    if (a.isEqual && _.isFunction(a.isEqual)) return a.isEqual(b);
680    if (b.isEqual && _.isFunction(b.isEqual)) return b.isEqual(a);
681    // Compare `[[Class]]` names.
682    var className = toString.call(a);
683    if (className != toString.call(b)) return false;
684    switch (className) {
685      // Strings, numbers, dates, and booleans are compared by value.
686      case '[object String]':
687        // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
688        // equivalent to `new String("5")`.
689        return a == String(b);
690      case '[object Number]':
691        // `NaN`s are equivalent, but non-reflexive. An `egal` comparison is performed for
692        // other numeric values.
693        return a != +a ? b != +b : (a == 0 ? 1 / a == 1 / b : a == +b);
694      case '[object Date]':
695      case '[object Boolean]':
696        // Coerce dates and booleans to numeric primitive values. Dates are compared by their
697        // millisecond representations. Note that invalid dates with millisecond representations
698        // of `NaN` are not equivalent.
699        return +a == +b;
700      // RegExps are compared by their source patterns and flags.
701      case '[object RegExp]':
702        return a.source == b.source &&
703               a.global == b.global &&
704               a.multiline == b.multiline &&
705               a.ignoreCase == b.ignoreCase;
706    }
707    if (typeof a != 'object' || typeof b != 'object') return false;
708    // Assume equality for cyclic structures. The algorithm for detecting cyclic
709    // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
710    var length = stack.length;
711    while (length--) {
712      // Linear search. Performance is inversely proportional to the number of
713      // unique nested structures.
714      if (stack[length] == a) return true;
715    }
716    // Add the first object to the stack of traversed objects.
717    stack.push(a);
718    var size = 0, result = true;
719    // Recursively compare objects and arrays.
720    if (className == '[object Array]') {
721      // Compare array lengths to determine if a deep comparison is necessary.
722      size = a.length;
723      result = size == b.length;
724      if (result) {
725        // Deep compare the contents, ignoring non-numeric properties.
726        while (size--) {
727          // Ensure commutative equality for sparse arrays.
728          if (!(result = size in a == size in b && eq(a[size], b[size], stack))) break;
729        }
730      }
731    } else {
732      // Objects with different constructors are not equivalent.
733      if ('constructor' in a != 'constructor' in b || a.constructor != b.constructor) return false;
734      // Deep compare objects.
735      for (var key in a) {
736        if (_.has(a, key)) {
737          // Count the expected number of properties.
738          size++;
739          // Deep compare each member.
740          if (!(result = _.has(b, key) && eq(a[key], b[key], stack))) break;
741        }
742      }
743      // Ensure that both objects contain the same number of properties.
744      if (result) {
745        for (key in b) {
746          if (_.has(b, key) && !(size--)) break;
747        }
748        result = !size;
749      }
750    }
751    // Remove the first object from the stack of traversed objects.
752    stack.pop();
753    return result;
754  }
755
756  // Perform a deep comparison to check if two objects are equal.
757  _.isEqual = function(a, b) {
758    return eq(a, b, []);
759  };
760
761  // Is a given array, string, or object empty?
762  // An "empty" object has no enumerable own-properties.
763  _.isEmpty = function(obj) {
764    if (_.isArray(obj) || _.isString(obj)) return obj.length === 0;
765    for (var key in obj) if (_.has(obj, key)) return false;
766    return true;
767  };
768
769  // Is a given value a DOM element?
770  _.isElement = function(obj) {
771    return !!(obj && obj.nodeType == 1);
772  };
773
774  // Is a given value an array?
775  // Delegates to ECMA5's native Array.isArray
776  _.isArray = nativeIsArray || function(obj) {
777    return toString.call(obj) == '[object Array]';
778  };
779
780  // Is a given variable an object?
781  _.isObject = function(obj) {
782    return obj === Object(obj);
783  };
784
785  // Is a given variable an arguments object?
786  _.isArguments = function(obj) {
787    return toString.call(obj) == '[object Arguments]';
788  };
789  if (!_.isArguments(arguments)) {
790    _.isArguments = function(obj) {
791      return !!(obj && _.has(obj, 'callee'));
792    };
793  }
794
795  // Is a given value a function?
796  _.isFunction = function(obj) {
797    return toString.call(obj) == '[object Function]';
798  };
799
800  // Is a given value a string?
801  _.isString = function(obj) {
802    return toString.call(obj) == '[object String]';
803  };
804
805  // Is a given value a number?
806  _.isNumber = function(obj) {
807    return toString.call(obj) == '[object Number]';
808  };
809
810  // Is the given value `NaN`?
811  _.isNaN = function(obj) {
812    // `NaN` is the only value for which `===` is not reflexive.
813    return obj !== obj;
814  };
815
816  // Is a given value a boolean?
817  _.isBoolean = function(obj) {
818    return obj === true || obj === false || toString.call(obj) == '[object Boolean]';
819  };
820
821  // Is a given value a date?
822  _.isDate = function(obj) {
823    return toString.call(obj) == '[object Date]';
824  };
825
826  // Is the given value a regular expression?
827  _.isRegExp = function(obj) {
828    return toString.call(obj) == '[object RegExp]';
829  };
830
831  // Is a given value equal to null?
832  _.isNull = function(obj) {
833    return obj === null;
834  };
835
836  // Is a given variable undefined?
837  _.isUndefined = function(obj) {
838    return obj === void 0;
839  };
840
841  // Has own property?
842  _.has = function(obj, key) {
843    return hasOwnProperty.call(obj, key);
844  };
845
846  // Utility Functions
847  // -----------------
848
849  // Run Underscore.js in *noConflict* mode, returning the `_` variable to its
850  // previous owner. Returns a reference to the Underscore object.
851  _.noConflict = function() {
852    root._ = previousUnderscore;
853    return this;
854  };
855
856  // Keep the identity function around for default iterators.
857  _.identity = function(value) {
858    return value;
859  };
860
861  // Run a function **n** times.
862  _.times = function (n, iterator, context) {
863    for (var i = 0; i < n; i++) iterator.call(context, i);
864  };
865
866  // Escape a string for HTML interpolation.
867  _.escape = function(string) {
868    return (''+string).replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;').replace(/'/g, '&#x27;').replace(/\//g,'&#x2F;');
869  };
870
871  // Add your own custom functions to the Underscore object, ensuring that
872  // they're correctly added to the OOP wrapper as well.
873  _.mixin = function(obj) {
874    each(_.functions(obj), function(name){
875      addToWrapper(name, _[name] = obj[name]);
876    });
877  };
878
879  // Generate a unique integer id (unique within the entire client session).
880  // Useful for temporary DOM ids.
881  var idCounter = 0;
882  _.uniqueId = function(prefix) {
883    var id = idCounter++;
884    return prefix ? prefix + id : id;
885  };
886
887  // By default, Underscore uses ERB-style template delimiters, change the
888  // following template settings to use alternative delimiters.
889  _.templateSettings = {
890    evaluate    : /<%([\s\S]+?)%>/g,
891    interpolate : /<%=([\s\S]+?)%>/g,
892    escape      : /<%-([\s\S]+?)%>/g
893  };
894
895  // When customizing `templateSettings`, if you don't want to define an
896  // interpolation, evaluation or escaping regex, we need one that is
897  // guaranteed not to match.
898  var noMatch = /.^/;
899
900  // Within an interpolation, evaluation, or escaping, remove HTML escaping
901  // that had been previously added.
902  var unescape = function(code) {
903    return code.replace(/\\\\/g, '\\').replace(/\\'/g, "'");
904  };
905
906  // JavaScript micro-templating, similar to John Resig's implementation.
907  // Underscore templating handles arbitrary delimiters, preserves whitespace,
908  // and correctly escapes quotes within interpolated code.
909  _.template = function(str, data) {
910    var c  = _.templateSettings;
911    var tmpl = 'var __p=[],print=function(){__p.push.apply(__p,arguments);};' +
912      'with(obj||{}){__p.push(\'' +
913      str.replace(/\\/g, '\\\\')
914         .replace(/'/g, "\\'")
915         .replace(c.escape || noMatch, function(match, code) {
916           return "',_.escape(" + unescape(code) + "),'";
917         })
918         .replace(c.interpolate || noMatch, function(match, code) {
919           return "'," + unescape(code) + ",'";
920         })
921         .replace(c.evaluate || noMatch, function(match, code) {
922           return "');" + unescape(code).replace(/[\r\n\t]/g, ' ') + ";__p.push('";
923         })
924         .replace(/\r/g, '\\r')
925         .replace(/\n/g, '\\n')
926         .replace(/\t/g, '\\t')
927         + "');}return __p.join('');";
928    var func = new Function('obj', '_', tmpl);
929    if (data) return func(data, _);
930    return function(data) {
931      return func.call(this, data, _);
932    };
933  };
934
935  // Add a "chain" function, which will delegate to the wrapper.
936  _.chain = function(obj) {
937    return _(obj).chain();
938  };
939
940  // The OOP Wrapper
941  // ---------------
942
943  // If Underscore is called as a function, it returns a wrapped object that
944  // can be used OO-style. This wrapper holds altered versions of all the
945  // underscore functions. Wrapped objects may be chained.
946  var wrapper = function(obj) { this._wrapped = obj; };
947
948  // Expose `wrapper.prototype` as `_.prototype`
949  _.prototype = wrapper.prototype;
950
951  // Helper function to continue chaining intermediate results.
952  var result = function(obj, chain) {
953    return chain ? _(obj).chain() : obj;
954  };
955
956  // A method to easily add functions to the OOP wrapper.
957  var addToWrapper = function(name, func) {
958    wrapper.prototype[name] = function() {
959      var args = slice.call(arguments);
960      unshift.call(args, this._wrapped);
961      return result(func.apply(_, args), this._chain);
962    };
963  };
964
965  // Add all of the Underscore functions to the wrapper object.
966  _.mixin(_);
967
968  // Add all mutator Array functions to the wrapper.
969  each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
970    var method = ArrayProto[name];
971    wrapper.prototype[name] = function() {
972      var wrapped = this._wrapped;
973      method.apply(wrapped, arguments);
974      var length = wrapped.length;
975      if ((name == 'shift' || name == 'splice') && length === 0) delete wrapped[0];
976      return result(wrapped, this._chain);
977    };
978  });
979
980  // Add all accessor Array functions to the wrapper.
981  each(['concat', 'join', 'slice'], function(name) {
982    var method = ArrayProto[name];
983    wrapper.prototype[name] = function() {
984      return result(method.apply(this._wrapped, arguments), this._chain);
985    };
986  });
987
988  // Start chaining a wrapped Underscore object.
989  wrapper.prototype.chain = function() {
990    this._chain = true;
991    return this;
992  };
993
994  // Extracts the result from a wrapped and chained object.
995  wrapper.prototype.value = function() {
996    return this._wrapped;
997  };
998
999}).call(this);