update `util/assign` for 5x gain

src/shared/utils.js

@@ -1,14 +1,6 @@
 export function noop() {}
 
-export function assign(target) {
+export function assign(tar, src) {
-	var k,
+	for (var k in src) tar[k] = src[k];
-		source,
+	return tar;
-		i = 1,
-		len = arguments.length;
-	for (; i < len; i++) {
-		source = arguments[i];
-		for (k in source) target[k] = source[k];
-	}
-
-	return target;
 }