added asyncRejectSeries from async.js

test/async.js

@@ -295,4 +295,33 @@ exports['async: asyncSelectSeries alias'] = function(test){
     test.done();
 };
 
+exports['async: asyncReject'] = function(test){
+    _.asyncReject([3,1,2], function(x, callback){
+        setTimeout(function(){callback(x % 2);}, x*25);
+    }, function(results){
+        test.same(results, [2]);
+        test.done();
+    });
+};
+
+exports['async: asyncReject original untouched'] = function(test){
+    var a = [3,1,2];
+    _.asyncReject(a, function(x, callback){
+        callback(x % 2);
+    }, function(results){
+        test.same(results, [2]);
+        test.same(a, [3,1,2]);
+        test.done();
+    });
+};
+
+exports['async: asyncRejectSeries'] = function(test){
+    _.asyncRejectSeries([3,1,2], function(x, callback){
+        setTimeout(function(){callback(x % 2);}, x*25);
+    }, function(results){
+        test.same(results, [2]);
+        test.done();
+    });
+};
+
 })(typeof exports === 'undefined' ? this['async_tests'] = {}: exports);

underscore.js

@@ -846,6 +846,30 @@
   _.asyncSelectSeries = _.asyncFilterSeries;
 
 
+  var _asyncReject = function (eachfn, arr, iterator, callback) {
+    var results = [];
+    arr = _.map(arr, function (x, i) {
+      return {index: i, value: x};
+    });
+    eachfn(arr, function (x, callback) {
+      iterator(x.value, function (v) {
+        if (!v) {
+          results.push(x);
+        }
+        callback();
+      });
+    }, function (err) {
+      callback(_.map(results.sort(function (a, b) {
+        return a.index - b.index;
+      }), function (x) {
+        return x.value;
+      }));
+    });
+  };
+  _.asyncReject = doParallel(_asyncReject);
+  _.asyncRejectSeries = doSeries(_asyncReject);
+
+
   // The OOP Wrapper
   // ---------------