Add options object to _.mixin. [closes #404]

lodash.js

@@ -3021,7 +3021,6 @@
       if (!isObject(object)) {
         return object;
       }
-
       // allows working with `_.reduce` and `_.reduceRight` without using
       // their `index` and `collection` arguments
       if (typeof args[2] != 'number') {
@@ -6214,51 +6213,71 @@
     }
 
     /**
-     * Adds function properties of a source object to the `lodash` function and
-     * chainable wrapper.
+     * Adds function properties of a source object to the destination object.
+     * If `object` is a function methods will be added to its prototype as well.
      *
      * @static
      * @memberOf _
      * @category Utilities
-     * @param {Object} object The object of function properties to add to `lodash`.
-     * @param {Object} object The object of function properties to add to `lodash`.
+     * @param {Function|Object} [object=lodash] object The destination object.
+     * @param {Object} source The object of functions to add.
+     * @param {Object} [options] The options object.
+     * @param {boolean} [options.chain=true] Specify whether the functions added are chainable.
      * @example
      *
-     * _.mixin({
-     *   'capitalize': function(string) {
-     *     return string.charAt(0).toUpperCase() + string.slice(1).toLowerCase();
-     *   }
-     * });
+     * function capitalize(string) {
+     *   return string.charAt(0).toUpperCase() + string.slice(1).toLowerCase();
+     * }
      *
+     * _.mixin({ 'capitalize': capitalize });
      * _.capitalize('fred');
      * // => 'Fred'
      *
      * _('fred').capitalize().value();
      * // => 'Fred'
+     *
+     * _.mixin({ 'capitalize': capitalize }, { 'chain': false });
+     * _('fred').capitalize();
+     * // => 'Fred'
      */
-    function mixin(object, source) {
-      var ctor = object,
-          isFunc = !source || isFunction(ctor);
+    function mixin(object, source, options) {
+      var chain = true,
+          methodNames = source && functions(source);
 
-      if (!source) {
+      if (!source || (!options && !methodNames.length)) {
+        if (options == null) {
+          options = source;
+        }
         ctor = lodashWrapper;
         source = object;
         object = lodash;
+        methodNames = functions(source);
       }
-      forEach(functions(source), function(methodName) {
+      if (options === false) {
+        chain = false;
+      } else if (isObject(options) && 'chain' in options) {
+        chain = options.chain;
+      }
+      var ctor = object,
+          isFunc = isFunction(ctor);
+
+      forEach(methodNames, function(methodName) {
         var func = object[methodName] = source[methodName];
         if (isFunc) {
           ctor.prototype[methodName] = function() {
-            var value = this.__wrapped__,
+            var chainAll = this.__chain__,
+                value = this.__wrapped__,
                 args = [value];
 
             push.apply(args, arguments);
             var result = func.apply(object, args);
-            if (value && typeof value == 'object' && value === result) {
-              return this;
+            if (chain || chainAll) {
+              if (value === result && isObject(result)) {
+                return this;
+              }
+              result = new ctor(result);
+              result.__chain__ = chainAll;
             }
-            result = new ctor(result);
-            result.__chain__ = this.__chain__;
             return result;
           };
         }
@@ -6994,20 +7013,15 @@
     lodash.include = contains;
     lodash.inject = reduce;
 
-    forOwn(lodash, function(func, methodName) {
-      if (!lodash.prototype[methodName]) {
-        lodash.prototype[methodName] = function() {
-          var args = [this.__wrapped__],
-              chainAll = this.__chain__;
-
-          push.apply(args, arguments);
-          var result = func.apply(lodash, args);
-          return chainAll
-            ? new lodashWrapper(result, chainAll)
-            : result;
-        };
-      }
-    });
+    mixin(function() {
+      var source = {}
+      forOwn(lodash, function(func, methodName) {
+        if (!lodash.prototype[methodName]) {
+          source[methodName] = func;
+        }
+      });
+      return source;
+    }(), false);
 
     /*--------------------------------------------------------------------------*/
 
@@ -7064,7 +7078,7 @@
       };
     });
 
-    // add `Array` functions that return the wrapped value
+    // add `Array` functions that return the existing wrapped value
     baseEach(['push', 'reverse', 'sort', 'unshift'], function(methodName) {
       var func = arrayRef[methodName];
       lodash.prototype[methodName] = function() {