<style>

#myDIV{

    border:1px solid black;

    width:300px;

    height:300px;

    background:url('/static/i/smiley.gif') no-repeat;

}

</style>

<p>点击“尝试一下”按钮扩大 DIV 元素的背景大小：</p>

<button onclick="myFunction()">尝试一下</button>

<div id="myDIV">

<h1>Hello</h1>

</div>

<script>

function myFunction(){

    document.getElementById("myDIV").style.backgroundSize = "60px 120px";

}

</script>