<!DOCTYLE html>
<html>
<head>
<meta charset="uft-8" />
<style>
#box {100px; height: 100px; background:#dfd; position:absolute; left:100px; top:100px;}
</style>
</head>
<body>
<button id="btn">600</button>
<div id="box"></div>
</body>
</html>
<script>
var btn = document.getElementById('btn');
var box = document.getElementById('box');
var target = 600;
var step = 0;
var timer = null;
btn.onclick = function () {
timer = setInterval(function () {
step =(target - box.offsetLeft)/10;//要放到定时器里面
step = step > 0 ? Math.ceil(step) : Math.floor(step);
box.style.left = box.offsetLeft+ step +'px';
if(box.offsetLeft>= target) {
clearInterval(timer)
}
console.log(box.offsetLeft)
},40)
}
</script>