requestAnimationFrame

@@ -160,42 +160,48 @@ $header.on('touchstart', 'a', function() {
     $(this).removeClass('highlight');
 });
 
-var lastTime = 0;
-var prefixes = 'webkit moz ms o'.split(' ');
+(function() {
+    var lastTime = 0,
+        prefixes = 'webkit moz ms o'.split(' '),
+        requestAnimationFrame = window.requestAnimationFrame,
+        cancelAnimationFrame = window.cancelAnimationFrame,
+        prefix,
+        i;
+
+    //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 (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'];
+    }
 
-var requestAnimationFrame = window.requestAnimationFrame;
-var cancelAnimationFrame = window.cancelAnimationFrame;
+    //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();
 
-var prefix;
+            //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);
 
-//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;
+            lastTime = currTime + timeToCall;
+            return id;
+        };
+
+        cancelAnimationFrame = function(id) {
+            window.clearTimeout(id);
+        };
     }
-    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 );
-    };
-}
+    window.requestAnimationFrame = requestAnimationFrame;
+    window.cancelAnimationFrame = cancelAnimationFrame;
+}());
 
 //暴露公共接口
 window.cookie = cookie;
@@ -209,7 +215,3 @@ window.getUid = getUid;
 window.getShoppingKey = getShoppingKey;
 
 window.rePosFooter = rePosFooter;
-
-window.requestAnimationFrame = requestAnimationFrame;
-
-window.cancelAnimationFrame = cancelAnimationFrame;