Sync objMap from upstream

src/vendor/core/objMap.js

@@ -0,0 +1,47 @@
+/**
+ * Copyright 2013 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * @providesModule objMap
+ */
+
+"use strict";
+
+/**
+ * For each key/value pair, invokes callback func and constructs a resulting
+ * object which contains, for every key in obj, values that are the result of
+ * of invoking the function:
+ *
+ *   func(value, key, iteration)
+ *
+ * @param {?object} obj Object to map keys over
+ * @param {function} func Invoked for each key/val pair.
+ * @param {?*} context
+ * @return {?object} Result of mapping or null if obj is falsey
+ */
+function objMap(obj, func, context) {
+  if (!obj) {
+    return null;
+  }
+  var i = 0;
+  var ret = {};
+  for (var key in obj) {
+    if (obj.hasOwnProperty(key)) {
+      ret[key] = func.call(context, obj[key], key, i++);
+    }
+  }
+  return ret;
+}
+
+module.exports = objMap;