| underscore.js | |
|---|---|
|  | (function() { | 
| Baseline setup |  | 
| Establish the root object,  |   var root = this; | 
| Save the previous value of the  |   var previousUnderscore = root._; | 
| Establish the object that gets returned to break out of a loop iteration. |   var breaker = {}; | 
| 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. |   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  |   if (typeof exports !== 'undefined') {
    if (typeof module !== 'undefined' && module.exports) {
      exports = module.exports = _;
    }
    exports._ = _;
  } else {
    root._ = _;
  } | 
| Current version. |   _.VERSION = '1.4.4'; | 
| Collection Functions |  | 
| The cornerstone, an  |   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 = _.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[results.length] = 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  |   _.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  |   _.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  |   _.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 = _.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[results.length] = 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 = _.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  |   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  |   _.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  |   _.pluck = function(obj, key) {
    return _.map(obj, function(value){ return value[key]; });
  }; | 
| Convenience version of a common use case of  |   _.where = function(obj, attrs, first) {
    if (_.isEmpty(attrs)) return first ? null : [];
    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  |   _.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: 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 || _.identity);
    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 convert anything iterable into a real, live array. |   _.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  |   _.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
 |   _.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  |   _.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  |   _.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  |   var flatten = function(input, shallow, output) {
    each(input, function(value) {
      if (_.isArray(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  |   _.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(concat.apply(ArrayProto, arguments));
  }; | 
| 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() {
    var args = slice.call(arguments);
    var length = _.max(_.pluck(args, 'length'));
    var results = new Array(length);
    for (var i = 0; i < length; i++) {
      results[i] = _.pluck(args, "" + i);
    }
    return results;
  }; | 
| Converts lists into objects. Pass either a single array of  |   _.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 = 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 = 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(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 |  | 
| Create a function bound to a given object (assigning  |   _.bind = function(func, context) {
    if (func.bind === nativeBind && nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
    var args = slice.call(arguments, 2);
    return function() {
      return func.apply(context, args.concat(slice.call(arguments)));
    };
  }; | 
| Partially apply a function by creating a version that has had some of its
arguments pre-filled, without changing its dynamic  |   _.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) funcs = _.functions(obj);
    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. |   _.throttle = function(func, wait) {
    var context, args, timeout, result;
    var previous = 0;
    var later = function() {
      previous = new Date;
      timeout = null;
      result = func.apply(context, args);
    };
    return function() {
      var now = new Date;
      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) {
        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  |   _.debounce = function(func, wait, immediate) {
    var timeout, result;
    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) {
    if (times <= 0) return 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  |   _.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[keys.length] = 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  |   _.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  |   _.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] == null) 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  |   var eq = function(a, b, aStack, bStack) { | 
| Identical objects are equal.  |     if (a === b) return a !== 0 || 1 / a == 1 / b; | 
| A strict comparison is necessary because  |     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  |     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,  |         return a == String(b);
      case '[object Number]': | 
| 
 |         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  |         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  |     var length = aStack.length;
    while (length--) { | 
| Linear search. Performance is inversely proportional to the number of unique nested structures. |       if (aStack[length] == a) return bStack[length] == b;
    } | 
| Add the first object to the stack of traversed objects. |     aStack.push(a);
    bStack.push(b);
    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 { | 
| Objects with different constructors are not equivalent, but  |       var aCtor = a.constructor, bCtor = b.constructor;
      if (aCtor !== bCtor && !(_.isFunction(aCtor) && (aCtor instanceof aCtor) &&
                               _.isFunction(bCtor) && (bCtor instanceof bCtor))) {
        return false;
      } | 
| 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  |   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  |   _.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  |   _.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(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; otherwise, return it. |   _.result = function(object, property) {
    if (object == null) return null;
    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  |   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();
  }; | 
| OOPIf 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);
 |