Merge pull request #2137 from megawac/partion-group

Implement partion via group

Author: jridgewell

underscore.js

@@ -391,9 +391,9 @@
   };
 
   // An internal function used for aggregate "group by" operations.
-  var group = function(behavior) {
+  var group = function(behavior, partition) {
     return function(obj, iteratee, context) {
-      var result = {};
+      var result = partition ? [[], []] : {};
       iteratee = cb(iteratee, context);
       _.each(obj, function(value, index) {
         var key = iteratee(value, index, obj);
@@ -438,14 +438,9 @@
 
   // Split a collection into two arrays: one whose elements all satisfy the given
   // predicate, and one whose elements all do not satisfy the predicate.
-  _.partition = function(obj, predicate, context) {
-    predicate = cb(predicate, context);
-    var pass = [], fail = [];
-    _.each(obj, function(value, key, obj) {
-      (predicate(value, key, obj) ? pass : fail).push(value);
-    });
-    return [pass, fail];
-  };
+  _.partition = group(function(result, value, pass) {
+    result[pass ? 0 : 1].push(value);
+  }, true);
 
   // Array Functions
   // ---------------