requestAnimationFrame

@@ -160,6 +160,43 @@ $header.on('touchstart', 'a', function() {
     $(this).removeClass('highlight');
     $(this).removeClass('highlight');
 });
 });
 
 
+var lastTime = 0;
+var prefixes = 'webkit moz ms o'.split(' ');
+
+var requestAnimationFrame = window.requestAnimationFrame;
+var cancelAnimationFrame = window.cancelAnimationFrame;
+
+var prefix;
+
+//通过遍历各浏览器前缀，来得到requestAnimationFrame和cancelAnimationFrame在当前浏览器的实现形式
+for( var i = 0; i < prefixes.length; i++ ) {
+    if ( requestAnimationFrame && cancelAnimationFrame ) {
+        break;
+    }
+    prefix = prefixes[i];
+    requestAnimationFrame = requestAnimationFrame || window[ prefix + 'RequestAnimationFrame' ];
+    cancelAnimationFrame  = cancelAnimationFrame  || window[ prefix + 'CancelAnimationFrame' ] || window[ prefix + 'CancelRequestAnimationFrame' ];
+}
+
+//如果当前浏览器不支持requestAnimationFrame和cancelAnimationFrame，则会退到setTimeout
+if ( !requestAnimationFrame || !cancelAnimationFrame ) {
+    requestAnimationFrame = function( callback, element ) {
+        var currTime = new Date().getTime();
+
+        //为了使setTimteout的尽可能的接近每秒60帧的效果
+        var timeToCall = Math.max( 0, 16 - ( currTime - lastTime ) );
+        var id = window.setTimeout( function() {
+            callback( currTime + timeToCall );
+        }, timeToCall );
+        lastTime = currTime + timeToCall;
+        return id;
+    };
+
+    cancelAnimationFrame = function( id ) {
+        window.clearTimeout( id );
+    };
+}
+
 //暴露公共接口
 //暴露公共接口
 window.cookie = cookie;
 window.cookie = cookie;
 
 
@@ -172,3 +209,7 @@ window.getUid = getUid;
 window.getShoppingKey = getShoppingKey;
 window.getShoppingKey = getShoppingKey;
 
 
 window.rePosFooter = rePosFooter;
 window.rePosFooter = rePosFooter;
+
+window.requestAnimationFrame = requestAnimationFrame;
+
+window.cancelAnimationFrame = cancelAnimationFrame;