<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>title</title>
<style>
* {
margin: 0;
padding: 0;
}
div {
width: 200px;
height: 150px;
background-color: pink;
border-radius: 100px;
}
</style>
</head>
<body>
<input type="button" value="变宽" id="btn" />
<div id="dv"></div>
<script src="common.js"></script>
<script>
my$("btn").onclick = function () {
var width = 200;
var timeId = setInterval(function () {
width += 10;
if (width == 800) {
clearInterval(timeId);
}
my$("dv").style.width = width + "px";
}, 100);
};
</script>
</body>
</html>
原文：https://www.cnblogs.com/jane-panyiyun/p/12029321.html