feat($sniffer): add hasEvent method for sniffing events

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src/ng/sniffer.js

@@ -12,13 +12,23 @@
  * @description
  * This is very simple implementation of testing browser's features.
  */
-function $SnifferProvider(){
-  this.$get = ['$window', function($window){
+function $SnifferProvider() {
+  this.$get = ['$window', function($window) {
+    var eventSupport = {};
+
     return {
       history: !!($window.history && $window.history.pushState),
       hashchange: 'onhashchange' in $window &&
                   // IE8 compatible mode lies
-                  (!$window.document.documentMode || $window.document.documentMode > 7)
+                  (!$window.document.documentMode || $window.document.documentMode > 7),
+      hasEvent: function(event) {
+        if (isUndefined(eventSupport[event])) {
+          var divElm = $window.document.createElement('div');
+          eventSupport[event] = 'on' + event in divElm;
+        }
+
+        return eventSupport[event];
+      }
     };
   }];
 }

test/ng/snifferSpec.js

@@ -30,4 +30,43 @@ describe('$sniffer', function() {
       expect(sniffer({onhashchange: true, document: {documentMode: 7}}).hashchange).toBe(false);
     });
   });
+
+
+  describe('hasEvent', function() {
+    var mockDocument, mockDivElement, $sniffer;
+
+    beforeEach(function() {
+      mockDocument = {createElement: jasmine.createSpy('createElement')};
+      mockDocument.createElement.andCallFake(function(elm) {
+        if (elm === 'div') return mockDivElement;
+      });
+
+      $sniffer = sniffer({document: mockDocument});
+    });
+
+
+    it('should return true if "oninput" is present in a div element', function() {
+      mockDivElement = {oninput: noop};
+
+      expect($sniffer.hasEvent('input')).toBe(true);
+    });
+
+
+    it('should return false if "oninput" is not present in a div element', function() {
+      mockDivElement = {};
+
+      expect($sniffer.hasEvent('input')).toBe(false);
+    });
+
+
+    it('should only create the element once', function() {
+      mockDivElement = {};
+
+      $sniffer.hasEvent('input');
+      $sniffer.hasEvent('input');
+      $sniffer.hasEvent('input');
+
+      expect(mockDocument.createElement).toHaveBeenCalledOnce();
+    });
+  });
 });