位置
				};

				MoveCommand.prototype.undo = function(){
					this.receiver.start( 'left', this.oldPos, 1000, 'strongEaseOut' );
			// 回到小球移动前记录的位置
		};
		var moveCommand;

		moveBtn.onclick = function(){
			var animate = new Animate( ball );
			moveCommand = new MoveCommand( animate, pos.value );
			moveCommand.execute();
		};
		cancelBtn.onclick = function(){
				moveCommand.undo(); // 撤销命令
			};
		</script>

	</body>
	</html>

	<html>
	<body>
		<