封装好的运动方法

function move(obj,val,target,dir,endFn){
val=parseInt(getStyle(obj,dir))<target?val:-val;
clearInterval(obj.timer);
obj.timer=setInterval(function(){
var speed=parseInt(getStyle(obj,dir))+val;
if(speed>=target&&val>0 || speed<=target&&val<0){
speed=target;
} 
obj.style[dir]=speed+'px';
if(speed==target){
clearInterval(obj.timer);
endFn&&endFn();
}
},30);
}