added asyncMap and asyncMapSeries from async.js

test/async.js

@@ -137,4 +137,63 @@ exports['async: asyncEachSeries alias'] = function (test) {
     test.done();
 };
 
+exports['async: asyncMap'] = function(test){
+    var call_order = [];
+    _.asyncMap([1,3,2], function(x, callback){
+        setTimeout(function(){
+            call_order.push(x);
+            callback(null, x*2);
+        }, x*25);
+    }, function(err, results){
+        test.same(call_order, [1,2,3]);
+        test.same(results, [2,6,4]);
+        test.done();
+    });
+};
+
+exports['async: asyncMap original untouched'] = function(test){
+    var a = [1,2,3];
+    _.asyncMap(a, function(x, callback){
+        callback(null, x*2);
+    }, function(err, results){
+        test.same(results, [2,4,6]);
+        test.same(a, [1,2,3]);
+        test.done();
+    });
+};
+
+exports['async: asyncMap error'] = function(test){
+    test.expect(1);
+    _.asyncMap([1,2,3], function(x, callback){
+        callback('error');
+    }, function(err, results){
+        test.equals(err, 'error');
+    });
+    setTimeout(test.done, 50);
+};
+
+exports['async: asyncMapSeries'] = function(test){
+    var call_order = [];
+    _.asyncMapSeries([1,3,2], function(x, callback){
+        setTimeout(function(){
+            call_order.push(x);
+            callback(null, x*2);
+        }, x*25);
+    }, function(err, results){
+        test.same(call_order, [1,3,2]);
+        test.same(results, [2,6,4]);
+        test.done();
+    });
+};
+
+exports['async: asyncMapSeries error'] = function(test){
+    test.expect(1);
+    _.asyncMapSeries([1,2,3], function(x, callback){
+        callback('error');
+    }, function(err, results){
+        test.equals(err, 'error');
+    });
+    setTimeout(test.done, 50);
+};
+
 })(typeof exports === 'undefined' ? this['async_tests'] = {}: exports);

underscore.js

@@ -759,6 +759,38 @@
   };
 
 
+  var doParallel = function (fn) {
+    return function () {
+      var args = Array.prototype.slice.call(arguments);
+      return fn.apply(null, [_.asyncForEach].concat(args));
+    };
+  };
+  var doSeries = function (fn) {
+    return function () {
+      var args = Array.prototype.slice.call(arguments);
+      return fn.apply(null, [_.asyncForEachSeries].concat(args));
+    };
+  };
+
+
+  var _asyncMap = 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 (err, v) {
+        results[x.index] = v;
+        callback(err);
+      });
+    }, function (err) {
+      callback(err, results);
+    });
+  };
+  _.asyncMap = doParallel(_asyncMap);
+  _.asyncMapSeries = doSeries(_asyncMap);
+
+
   // The OOP Wrapper
   // ---------------