refactor(util): use Object.assign polyfill

ionic/util/test/util.spec.ts

@@ -5,23 +5,10 @@ export function run() {
 
     it('should extend simple', () => {
       var obj = { a: '0', c: '0' };
-      expect( util.extend(obj, { a: '1', b: '2' }) ).toBe(obj);
+      expect( util.assign(obj, { a: '1', b: '2' }) ).toBe(obj);
       expect(obj).toEqual({ a: '1', b: '2', c: '0' });
     });
 
-    it('should extend complex', () => {
-      expect(util.extend(
-        { a: '0', b: '0' },
-        { b: '1', c: '1' },
-        { c: '2', d: '2' }
-      )).toEqual({
-        a: '0',
-        b: '1',
-        c: '2',
-        d: '2'
-      });
-    });
-
   });
 
   describe('defaults', function() {
@@ -29,7 +16,7 @@ export function run() {
     it('should simple defaults', () => {
       var obj = { a: '1' };
       expect(util.defaults(obj, { a: '2', b: '2' })).toBe(obj);
-      expect(obj).toEqual({ 
+      expect(obj).toEqual({
         a: '1', b: '2'
       });
     });

ionic/util/util.ts

@@ -12,13 +12,26 @@ export function clamp(min, n, max) {
   return Math.max(min, Math.min(n, max));
 }
 
+// polyfill for Object.assign
+var _assign: any;
+if (typeof Object.assign !== 'function') {
+  // use the old-school shallow extend method
+  _assign = _baseExtend;
+} else {
+  // use the built in ES6 Object.assign method
+  _assign = Object.assign;
+}
+
 /**
- * Extend the destination with an arbitrary number of other objects.
- * @param dst the destination
- * @param ... the param objects
+ * The assign() method is used to copy the values of all enumerable own
+ * properties from one or more source objects to a target object. It will
+ * return the target object. When available, this method will use
+ * `Object.assign()` under-the-hood.
+ * @param target  The target object
+ * @param source  The source object
  */
-export function extend(dst: any, ...args: any[]) {
-  return _baseExtend(dst, [].slice.call(arguments, 1), false);
+export function assign(target: any, source: any): any {
+  return _assign(target, source);
 }
 
 /**
@@ -30,7 +43,7 @@ export function merge(dst: any, ...args: any[]) {
   return _baseExtend(dst, [].slice.call(arguments, 1), true);
 }
 
-function _baseExtend(dst, objs, deep) {
+function _baseExtend(dst, objs, deep = false) {
   for (var i = 0, ii = objs.length; i < ii; ++i) {
     var obj = objs[i];
     if (!obj || !isObject(obj) && !isFunction(obj)) continue;