js之封装函数实现元素的左右来回移动

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			div {
				position: absolute;
				left: 0px;
				width: 200px;
				height: 200px;
				background: greenyellow;
			}
		</style>
		<script src="./getby.js"></script>
		<script type="text/javascript">
			window.onload = function() {
				var btnS = document.getElementsByTagName('button');
				var div = document.querySelector('div');
				btnS[0].onclick = function(){
					move(div,1000,10);
				}
				btnS[1].onclick = function(){
					move(div,0,10);
				}
			}
		</script>
	</head>
	<body>
		<button type="button">去吧</button>
		<button type="button">回来</button>
		<div></div>
	</body>
</html>

getby.js

/* Created By dyh 2020.3.28 */
//获取任意元素的非行内样式 用法：getStyle(元素,属性);
function getStyle(ele, attr){
	if (ele.currentStyle == undefined) {
		//标准浏览器
		var bg = getComputedStyle(ele)[attr];
		return bg;
	} else {
		//ie8-
		var bg = ele.currentStyle[attr];
		return bg;
	}
}

//封装一个函数，用来执行任意元素正反两个方向的动画 用法：move(元素,终点,步长);
var timer = null; //定时器id
function move(ele, end, step) {
	//清除定时器防止叠加
	clearInterval(timer);
	//获取起点
	var start = parseInt(getStyle(ele, 'left'));
	//处理步长 判断向前 向后
	if (end > start) {
		step = step;
	} else if (end < start) {
		step = -step;
	}
	//定时器
	timer = setInterval(function() {
		//计算下一步落点
		start += step;
		//重点结束
		if (start >= end && step > 0) {
			//正向移动
			start = end;
			clearInterval(timer);
		} else if (start <= end && step < 0) {
			//负方向移动
			start = end;
			clearInterval(timer);
		}
		ele.style.left = start + 'px';
	}, 20);
}