added _.transform definition

lodash/lodash-tests.ts

@@ -699,6 +699,18 @@ result = <any>_.pick({ 'name': 'moe', '_userid': 'moe1' }, function(value, key)
   return key.charAt(0) != '_';
 });
 
+result = <any>_.transform([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], function(result, num) {
+  num *= num;
+  if (num % 2) {
+    return result.push(num) < 3;
+  }
+});
+// → [1, 9, 25]
+
+result = <any>_.transform({ 'a': 1, 'b': 2, 'c': 3 }, function(result, num, key) {
+  result[key] = num * 3;
+});
+
 ////////////////////////////////////////////////////////////////////////////////////////
 //WHAT'S LEFT
 ////////////////////////////////////////////////////////////////////////////////////////

lodash/lodash.d.ts

@@ -2678,7 +2678,23 @@ declare module _ {
 		callback: ObjectIterator<any, boolean>,
 		thisArg?: any): any;
 	
-
+	/**
+	* An alternative to _.reduce this method transforms object to a new accumulator object which is 
+	* the result of running each of its elements through a callback, with each callback execution 
+	* potentially mutating the accumulator object. The callback is bound to thisArg and invoked with 
+	* four arguments; (accumulator, value, key, object). Callbacks may exit iteration early by 
+	* explicitly returning false.
+	* @param collection The collection to iterate over.
+	* @param callback The function called per iteration.
+	* @param accumulator The custom accumulator value.
+	* @param thisArg The this binding of callback.
+	* @return The accumulated value.
+	**/
+	export function transform<T>(
+		collection: Collection<T>,
+		callback?: MemoIterator<T, any>,
+		accumulator?: any,
+		thisArg?: any): any