underscore.js in ultimate-base-0.7.2

- old
+ new

@@ -1,17 +1,16 @@
-// Underscore.js 1.4.4
-// ===================
+//     Underscore.js 1.5.2
+//     http://underscorejs.org
+//     (c) 2009-2014 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
+//     Underscore may be freely distributed under the MIT license.
 
-// > http://underscorejs.org
-// > (c) 2009-2013 Jeremy Ashkenas, DocumentCloud Inc.
-// > Underscore may be freely distributed under the MIT license.
-
-// Baseline setup
-// --------------
 (function() {
 
-  // Establish the root object, `window` in the browser, or `global` on the server.
+  // Baseline setup
+  // --------------
+
+  // Establish the root object, `window` in the browser, or `exports` on the server.
   var root = this;
 
   // Save the previous value of the `_` variable.
   var previousUnderscore = root._;
 
@@ -19,16 +18,22 @@
   var breaker = {};
 
   // Save bytes in the minified (but not gzipped) version:
   var ArrayProto = Array.prototype, ObjProto = Object.prototype, FuncProto = Function.prototype;
 
+  //use the faster Date.now if available.
+  var getTime = (Date.now || function() {
+    return new Date().getTime();
+  });
+
   // 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;
+  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,
@@ -63,11 +68,11 @@
   } else {
     root._ = _;
   }
 
   // Current version.
-  _.VERSION = '1.4.4';
+  _.VERSION = '1.5.2';
 
   // Collection Functions
   // --------------------
 
   // The cornerstone, an `each` implementation, aka `forEach`.
@@ -76,18 +81,17 @@
   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++) {
+      for (var i = 0, length = obj.length; i < length; 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;
-        }
+      var keys = _.keys(obj);
+      for (var i = 0, length = keys.length; i < length; i++) {
+        if (iterator.call(context, obj[keys[i]], keys[i], obj) === breaker) return;
       }
     }
   };
 
   // Return the results of applying the iterator to each element.
@@ -95,11 +99,11 @@
   _.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);
+      results.push(iterator.call(context, value, index, list));
     });
     return results;
   };
 
   var reduceError = 'Reduce of empty array with no initial value';
@@ -170,11 +174,11 @@
   _.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;
+      if (iterator.call(context, value, index, list)) results.push(value);
     });
     return results;
   };
 
   // Return all the elements for which a truth test fails.
@@ -231,17 +235,16 @@
     });
   };
 
   // Convenience version of a common use case of `map`: fetching a property.
   _.pluck = function(obj, key) {
-    return _.map(obj, function(value){ return value[key]; });
+    return _.map(obj, _.property(key));
   };
 
   // Convenience version of a common use case of `filter`: selecting only objects
   // containing specific `key:value` pairs.
   _.where = function(obj, attrs, first) {
-    if (_.isEmpty(attrs)) return first ? null : [];
     return _[first ? 'find' : 'filter'](obj, function(value) {
       for (var key in attrs) {
         if (attrs[key] !== value[key]) return false;
       }
       return true;
@@ -254,20 +257,20 @@
     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
+  // See [WebKit Bug 80797](https://bugs.webkit.org/show_bug.cgi?id=80797)
   _.max = function(obj, iterator, context) {
     if (!iterator && _.isArray(obj) && obj[0] === +obj[0] && obj.length < 65535) {
       return Math.max.apply(Math, obj);
     }
     if (!iterator && _.isEmpty(obj)) return -Infinity;
     var result = {computed : -Infinity, value: -Infinity};
     each(obj, function(value, index, list) {
       var computed = iterator ? iterator.call(context, value, index, list) : value;
-      computed >= result.computed && (result = {value : value, computed : computed});
+      computed > result.computed && (result = {value : value, computed : computed});
     });
     return result.value;
   };
 
   // Return the minimum element (or element-based computation).
@@ -282,11 +285,12 @@
       computed < result.computed && (result = {value : value, computed : computed});
     });
     return result.value;
   };
 
-  // Shuffle an array.
+  // Shuffle an array, using the modern version of the
+  // [Fisher-Yates shuffle](http://en.wikipedia.org/wiki/Fisher–Yates_shuffle).
   _.shuffle = function(obj) {
     var rand;
     var index = 0;
     var shuffled = [];
     each(obj, function(value) {
@@ -295,78 +299,94 @@
       shuffled[rand] = value;
     });
     return shuffled;
   };
 
+  // Sample **n** random values from a collection.
+  // If **n** is not specified, returns a single random element.
+  // The internal `guard` argument allows it to work with `map`.
+  _.sample = function(obj, n, guard) {
+    if (n == null || guard) {
+      if (obj.length !== +obj.length) obj = _.values(obj);
+      return obj[_.random(obj.length - 1)];
+    }
+    return _.shuffle(obj).slice(0, Math.max(0, n));
+  };
+
   // An internal function to generate lookup iterators.
   var lookupIterator = function(value) {
-    return _.isFunction(value) ? value : function(obj){ return obj[value]; };
+    if (value == null) return _.identity;
+    if (_.isFunction(value)) return value;
+    return _.property(value);
   };
 
   // Sort the object's values by a criterion produced by an iterator.
-  _.sortBy = function(obj, value, context) {
-    var iterator = lookupIterator(value);
+  _.sortBy = function(obj, iterator, context) {
+    iterator = lookupIterator(iterator);
     return _.pluck(_.map(obj, function(value, index, list) {
       return {
-        value : value,
-        index : index,
-        criteria : iterator.call(context, value, index, list)
+        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;
+      return left.index - right.index;
     }), '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;
+  var group = function(behavior) {
+    return function(obj, iterator, context) {
+      var result = {};
+      iterator = lookupIterator(iterator);
+      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);
-    });
-  };
+  _.groupBy = group(function(result, key, value) {
+    _.has(result, key) ? result[key].push(value) : result[key] = [value];
+  });
 
+  // Indexes the object's values by a criterion, similar to `groupBy`, but for
+  // when you know that your index values will be unique.
+  _.indexBy = group(function(result, key, value) {
+    result[key] = 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]++;
-    });
-  };
+  _.countBy = group(function(result, key) {
+    _.has(result, key) ? result[key]++ : result[key] = 1;
+  });
 
   // 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);
+    iterator = 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.
+  // Safely create a real, live array from anything iterable.
   _.toArray = function(obj) {
     if (!obj) return [];
     if (_.isArray(obj)) return slice.call(obj);
     if (obj.length === +obj.length) return _.map(obj, _.identity);
     return _.values(obj);
@@ -384,11 +404,13 @@
   // Get the first element of an array. Passing **n** will return the first N
   // values in the array. Aliased as `head` and `take`. The **guard** check
   // allows it to work with `_.map`.
   _.first = _.head = _.take = function(array, n, guard) {
     if (array == null) return void 0;
-    return (n != null) && !guard ? slice.call(array, 0, n) : array[0];
+    if ((n == null) || guard) return array[0];
+    if (n < 0) return [];
+    return slice.call(array, 0, n);
   };
 
   // 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
@@ -399,15 +421,12 @@
 
   // Get the last element of an array. Passing **n** will return the last N
   // values in the array. The **guard** check allows it to work with `_.map`.
   _.last = function(array, n, guard) {
     if (array == null) return void 0;
-    if ((n != null) && !guard) {
-      return slice.call(array, Math.max(array.length - n, 0));
-    } else {
-      return array[array.length - 1];
-    }
+    if ((n == null) || guard) return array[array.length - 1];
+    return slice.call(array, Math.max(array.length - n, 0));
   };
 
   // Returns everything but the first entry of the array. Aliased as `tail` and `drop`.
   // Especially useful on the arguments object. Passing an **n** will return
   // the rest N values in the array. The **guard**
@@ -421,21 +440,24 @@
     return _.filter(array, _.identity);
   };
 
   // Internal implementation of a recursive `flatten` function.
   var flatten = function(input, shallow, output) {
+    if (shallow && _.every(input, _.isArray)) {
+      return concat.apply(output, input);
+    }
     each(input, function(value) {
-      if (_.isArray(value)) {
+      if (_.isArray(value) || _.isArguments(value)) {
         shallow ? push.apply(output, value) : flatten(value, shallow, output);
       } else {
         output.push(value);
       }
     });
     return output;
   };
 
-  // Return a completely flattened version of an array.
+  // Flatten out an array, either recursively (by default), or just one level.
   _.flatten = function(array, shallow) {
     return flatten(array, shallow, []);
   };
 
   // Return a version of the array that does not contain the specified value(s).
@@ -465,11 +487,11 @@
   };
 
   // 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));
+    return _.uniq(_.flatten(arguments, true));
   };
 
   // Produce an array that contains every item shared between all the
   // passed-in arrays.
   _.intersection = function(array) {
@@ -489,26 +511,25 @@
   };
 
   // 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 length = _.max(_.pluck(arguments, "length").concat(0));
     var results = new Array(length);
     for (var i = 0; i < length; i++) {
-      results[i] = _.pluck(args, "" + i);
+      results[i] = _.pluck(arguments, '' + i);
     }
     return results;
   };
 
   // Converts lists into objects. Pass either a single array of `[key, value]`
   // pairs, or two parallel arrays of the same length -- one of keys, and one of
   // the corresponding values.
   _.object = function(list, values) {
     if (list == null) return {};
     var result = {};
-    for (var i = 0, l = list.length; i < l; i++) {
+    for (var i = 0, length = list.length; i < length; i++) {
       if (values) {
         result[list[i]] = values[i];
       } else {
         result[list[i][0]] = list[i][1];
       }
@@ -522,21 +543,21 @@
   // Delegates to **ECMAScript 5**'s native `indexOf` if available.
   // If the array is large and already in sort order, pass `true`
   // for **isSorted** to use binary search.
   _.indexOf = function(array, item, isSorted) {
     if (array == null) return -1;
-    var i = 0, l = array.length;
+    var i = 0, length = array.length;
     if (isSorted) {
       if (typeof isSorted == 'number') {
-        i = (isSorted < 0 ? Math.max(0, l + isSorted) : isSorted);
+        i = (isSorted < 0 ? Math.max(0, length + 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;
+    for (; i < length; i++) if (array[i] === item) return i;
     return -1;
   };
 
   // Delegates to **ECMAScript 5**'s native `lastIndexOf` if available.
   _.lastIndexOf = function(array, item, from) {
@@ -558,50 +579,70 @@
       stop = start || 0;
       start = 0;
     }
     step = arguments[2] || 1;
 
-    var len = Math.max(Math.ceil((stop - start) / step), 0);
+    var length = Math.max(Math.ceil((stop - start) / step), 0);
     var idx = 0;
-    var range = new Array(len);
+    var range = new Array(length);
 
-    while(idx < len) {
+    while(idx < length) {
       range[idx++] = start;
       start += step;
     }
 
     return range;
   };
 
   // Function (ahem) Functions
   // ------------------
 
+  // Reusable constructor function for prototype setting.
+  var ctor = function(){};
+
   // Create a function bound to a given object (assigning `this`, and arguments,
   // optionally). Delegates to **ECMAScript 5**'s native `Function.bind` if
   // available.
   _.bind = function(func, context) {
-    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)));
+    var args, bound;
+    if (nativeBind && func.bind === nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
+    if (!_.isFunction(func)) throw new TypeError;
+    args = slice.call(arguments, 2);
+    return bound = function() {
+      if (!(this instanceof bound)) return func.apply(context, args.concat(slice.call(arguments)));
+      ctor.prototype = func.prototype;
+      var self = new ctor;
+      ctor.prototype = null;
+      var result = func.apply(self, args.concat(slice.call(arguments)));
+      if (Object(result) === result) return result;
+      return self;
     };
   };
 
   // Partially apply a function by creating a version that has had some of its
-  // arguments pre-filled, without changing its dynamic `this` context.
+  // arguments pre-filled, without changing its dynamic `this` context. _ acts
+  // as a placeholder, allowing any combination of arguments to be pre-filled.
   _.partial = function(func) {
-    var args = slice.call(arguments, 1);
+    var boundArgs = slice.call(arguments, 1);
     return function() {
-      return func.apply(this, args.concat(slice.call(arguments)));
+      var args = slice.call(boundArgs);
+      _.each(arguments, function(arg) {
+        var index = args.indexOf(_);
+        args[index >= 0 ? index : args.length] = arg;
+      });
+      return func.apply(this, _.map(args, function(value) {
+        return value === _ ? void 0 : value;
+      }));
     };
   };
 
-  // Bind all of an object's methods to that object. Useful for ensuring that
-  // all callbacks defined on an object belong to it.
+  // Bind a number of an object's methods to that object. Remaining arguments
+  // are the method names to be bound. 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);
+    if (funcs.length === 0) throw new Error("bindAll must be passed function names");
     each(funcs, function(f) { obj[f] = _.bind(obj[f], obj); });
     return obj;
   };
 
   // Memoize an expensive function by storing its results.
@@ -626,30 +667,38 @@
   _.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;
+  // during a given window of time. Normally, the throttled function will run
+  // as much as it can, without ever going more than once per `wait` duration;
+  // but if you'd like to disable the execution on the leading edge, pass
+  // `{leading: false}`. To disable execution on the trailing edge, ditto.
+  _.throttle = function(func, wait, options) {
+    var context, args, result;
+    var timeout = null;
     var previous = 0;
+    options || (options = {});
     var later = function() {
-      previous = new Date;
+      previous = options.leading === false ? 0 : getTime();
       timeout = null;
       result = func.apply(context, args);
+      context = args = null;
     };
     return function() {
-      var now = new Date;
+      var now = getTime();
+      if (!previous && options.leading === false) previous = now;
       var remaining = wait - (now - previous);
       context = this;
       args = arguments;
       if (remaining <= 0) {
         clearTimeout(timeout);
         timeout = null;
         previous = now;
         result = func.apply(context, args);
-      } else if (!timeout) {
+        context = args = null;
+      } else if (!timeout && options.trailing !== false) {
         timeout = setTimeout(later, remaining);
       }
       return result;
     };
   };
@@ -657,21 +706,36 @@
   // Returns a function, that, as long as it continues to be invoked, will not
   // be triggered. The function will be called after it stops being called for
   // N milliseconds. If `immediate` is passed, trigger the function on the
   // leading edge, instead of the trailing.
   _.debounce = function(func, wait, immediate) {
-    var timeout, result;
+    var timeout, args, context, timestamp, result;
     return function() {
-      var context = this, args = arguments;
+      context = this;
+      args = arguments;
+      timestamp = getTime();
       var later = function() {
-        timeout = null;
-        if (!immediate) result = func.apply(context, args);
+        var last = getTime() - timestamp;
+        if (last < wait) {
+          timeout = setTimeout(later, wait - last);
+        } else {
+          timeout = null;
+          if (!immediate) {
+            result = func.apply(context, args);
+            context = args = null;
+          }
+        }
       };
       var callNow = immediate && !timeout;
-      clearTimeout(timeout);
-      timeout = setTimeout(later, wait);
-      if (callNow) result = func.apply(context, args);
+      if (!timeout) {
+        timeout = setTimeout(later, wait);
+      }
+      if (callNow) {
+        result = func.apply(context, args);
+        context = args = null;
+      }
+
       return result;
     };
   };
 
   // Returns a function that will be executed at most one time, no matter how
@@ -689,15 +753,11 @@
 
   // 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);
-    };
+    return _.partial(wrapper, func);
   };
 
   // Returns a function that is the composition of a list of functions, each
   // consuming the return value of the function that follows.
   _.compose = function() {
@@ -711,11 +771,10 @@
     };
   };
 
   // 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);
       }
     };
@@ -727,32 +786,43 @@
   // Retrieve the names of an object's properties.
   // Delegates to **ECMAScript 5**'s native `Object.keys`
   _.keys = nativeKeys || function(obj) {
     if (obj !== Object(obj)) throw new TypeError('Invalid object');
     var keys = [];
-    for (var key in obj) if (_.has(obj, key)) keys[keys.length] = key;
+    for (var key in obj) if (_.has(obj, key)) keys.push(key);
     return keys;
   };
 
   // Retrieve the values of an object's properties.
   _.values = function(obj) {
-    var values = [];
-    for (var key in obj) if (_.has(obj, key)) values.push(obj[key]);
+    var keys = _.keys(obj);
+    var length = keys.length;
+    var values = new Array(length);
+    for (var i = 0; i < length; i++) {
+      values[i] = obj[keys[i]];
+    }
     return values;
   };
 
   // Convert an object into a list of `[key, value]` pairs.
   _.pairs = function(obj) {
-    var pairs = [];
-    for (var key in obj) if (_.has(obj, key)) pairs.push([key, obj[key]]);
+    var keys = _.keys(obj);
+    var length = keys.length;
+    var pairs = new Array(length);
+    for (var i = 0; i < length; i++) {
+      pairs[i] = [keys[i], obj[keys[i]]];
+    }
     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;
+    var keys = _.keys(obj);
+    for (var i = 0, length = keys.length; i < length; i++) {
+      result[obj[keys[i]]] = keys[i];
+    }
     return result;
   };
 
   // Return a sorted list of the function names available on the object.
   // Aliased as `methods`
@@ -799,11 +869,11 @@
   // 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];
+          if (obj[prop] === void 0) obj[prop] = source[prop];
         }
       }
     });
     return obj;
   };
@@ -823,11 +893,11 @@
   };
 
   // Internal recursive comparison function for `isEqual`.
   var eq = function(a, b, aStack, bStack) {
     // Identical objects are equal. `0 === -0`, but they aren't identical.
-    // See the Harmony `egal` proposal: http://wiki.ecmascript.org/doku.php?id=harmony:egal.
+    // See the [Harmony `egal` proposal](http://wiki.ecmascript.org/doku.php?id=harmony:egal).
     if (a === b) return a !== 0 || 1 / a == 1 / b;
     // A strict comparison is necessary because `null == undefined`.
     if (a == null || b == null) return a === b;
     // Unwrap any wrapped objects.
     if (a instanceof _) a = a._wrapped;
@@ -865,10 +935,18 @@
     while (length--) {
       // Linear search. Performance is inversely proportional to the number of
       // unique nested structures.
       if (aStack[length] == a) return bStack[length] == b;
     }
+    // Objects with different constructors are not equivalent, but `Object`s
+    // from different frames are.
+    var aCtor = a.constructor, bCtor = b.constructor;
+    if (aCtor !== bCtor && !(_.isFunction(aCtor) && (aCtor instanceof aCtor) &&
+                             _.isFunction(bCtor) && (bCtor instanceof bCtor))
+                        && ('constructor' in a && 'constructor' in b)) {
+      return false;
+    }
     // Add the first object to the stack of traversed objects.
     aStack.push(a);
     bStack.push(b);
     var size = 0, result = true;
     // Recursively compare objects and arrays.
@@ -881,17 +959,10 @@
         while (size--) {
           if (!(result = eq(a[size], b[size], aStack, bStack))) break;
         }
       }
     } else {
-      // Objects with different constructors are not equivalent, but `Object`s
-      // from different frames are.
-      var aCtor = a.constructor, bCtor = b.constructor;
-      if (aCtor !== bCtor && !(_.isFunction(aCtor) && (aCtor instanceof aCtor) &&
-                               _.isFunction(bCtor) && (bCtor instanceof bCtor))) {
-        return false;
-      }
       // Deep compare objects.
       for (var key in a) {
         if (_.has(a, key)) {
           // Count the expected number of properties.
           size++;
@@ -1009,13 +1080,25 @@
   // Keep the identity function around for default iterators.
   _.identity = function(value) {
     return value;
   };
 
+  _.constant = function(value) {
+    return function () {
+      return value;
+    };
+  };
+
+  _.property = function(key) {
+    return function(obj) {
+      return obj[key];
+    };
+  };
+
   // Run a function **n** times.
   _.times = function(n, iterator, context) {
-    var accum = Array(n);
+    var accum = Array(Math.max(0, n));
     for (var i = 0; i < n; i++) accum[i] = iterator.call(context, i);
     return accum;
   };
 
   // Return a random integer between min and max (inclusive).
@@ -1032,12 +1115,11 @@
     escape: {
       '&': '&amp;',
       '<': '&lt;',
       '>': '&gt;',
       '"': '&quot;',
-      "'": '&#x27;',
-      '/': '&#x2F;'
+      "'": '&#x27;'
     }
   };
   entityMap.unescape = _.invert(entityMap.escape);
 
   // Regexes containing the keys and values listed immediately above.
@@ -1054,21 +1136,21 @@
         return entityMap[method][match];
       });
     };
   });
 
-  // If the value of the named property is a function then invoke it;
-  // otherwise, return it.
+  // If the value of the named `property` is a function then invoke it with the
+  // `object` as context; otherwise, return it.
   _.result = function(object, property) {
-    if (object == null) return null;
+    if (object == null) return void 0;
     var value = object[property];
     return _.isFunction(value) ? value.call(object) : value;
   };
 
   // Add your own custom functions to the Underscore object.
   _.mixin = function(obj) {
-    each(_.functions(obj), function(name){
+    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));
@@ -1222,6 +1304,18 @@
       return this._wrapped;
     }
 
   });
 
+  // AMD registration happens at the end for compatibility with AMD loaders
+  // that may not enforce next-turn semantics on modules. Even though general
+  // practice for AMD registration is to be anonymous, underscore registers
+  // as a named module because, like jQuery, it is a base library that is
+  // popular enough to be bundled in a third party lib, but not be part of
+  // an AMD load request. Those cases could generate an error when an
+  // anonymous define() is called outside of a loader request.
+  if (typeof define === 'function' && define.amd) {
+    define('underscore', [], function() {
+      return _;
+    });
+  }
 }).call(this);