perf(jqLite): implement and use the `empty` method in place of `html(‘’)`

jQuery's elem.html('') is way slower than elem.empty(). As clearing
element contents happens quite often in certain scenarios, switching
to using .empty() provides a significant performance boost when using
Angular with jQuery.

Closes #4457

1 files changed, 23 insertions, 2 deletions

diff --git a/test/jqLiteSpec.js b/test/jqLiteSpec.js
index 09be1c1c..c4f47dcd 100644
--- a/test/jqLiteSpec.js
+++ b/test/jqLiteSpec.js
@@ -322,7 +322,7 @@ describe('jqLite', function() {
     });
 
 
-    it('should emit $destroy event if an element is removed via html()', inject(function(log) {
+    it('should emit $destroy event if an element is removed via html(\'\')', inject(function(log) {
       var element = jqLite('<div><span>x</span></div>');
       element.find('span').on('$destroy', log.fn('destroyed'));
 
@@ -333,6 +333,17 @@ describe('jqLite', function() {
     }));
 
 
+    it('should emit $destroy event if an element is removed via empty()', inject(function(log) {
+      var element = jqLite('<div><span>x</span></div>');
+      element.find('span').on('$destroy', log.fn('destroyed'));
+
+      element.empty();
+
+      expect(element.html()).toBe('');
+      expect(log).toEqual('destroyed');
+    }));
+
+
     it('should retrieve all data if called without params', function() {
       var element = jqLite(a);
       expect(element.data()).toEqual({});
@@ -786,7 +797,7 @@ describe('jqLite', function() {
     });
 
 
-    it('should read/write value', function() {
+    it('should read/write a value', function() {
       var element = jqLite('<div>abc</div>');
       expect(element.length).toEqual(1);
       expect(element[0].innerHTML).toEqual('abc');
@@ -797,6 +808,16 @@ describe('jqLite', function() {
   });
 
 
+  describe('empty', function() {
+    it('should write a value', function() {
+      var element = jqLite('<div>abc</div>');
+      expect(element.length).toEqual(1);
+      expect(element.empty() == element).toBeTruthy();
+      expect(element.html()).toEqual('');
+    });
+  });
+
+
   describe('on', function() {
     it('should bind to window on hashchange', function() {
       if (jqLite.fn) return; // don't run in jQuery