效果：

缓动动画原理_HTML+CSS+JS

代码：

<!DOCTYPE html>
<html>
<head>
	<title>demo1</title>
	<style type="text/css">
		div	{
			width: 100px;
			height: 100px;
			background-color: pink;
			position: absolute;
			left: 0px;
		}
	</style>
</head>
<body>
	<button id="btn">开始</button>
	<div id="box"></div>
</body>
</html>
<script type="text/javascript">
	var btn = document.getElementById("btn");
	var box = document.getElementById("box");
	var target = 400;
	var timer = null;
	btn.onclick = function(){
		timer = setInterval(function(){
			//盒子本身得位置 + 步长(不断变化)
			var step = (target - box.offsetLeft) / 10;
			step = step > 0 ? Math.ceil(step) : Math.floor(step);
			box.style.left = box.offsetLeft + step + "px";
			if (box.offsetLeft == target) {
				clearInterval(timer);
				alert("到位置了");
			}
		},30);
	}
</script>