在线运行代码 - 菜鸟教程

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(cainiaoplay.com)</title>
<script>
function changeSize(){
	document.getElementById("mySelect").size=4;
}
</script>
</head>
<body>

<form>
<select id="mySelect">
<option>苹果</option>
<option>香蕉</option>
<option>橙子</option>
<option>甜瓜</option>
</select>
<input type="button" onclick="changeSize()" value="修改列表大小">
</form>

</body>
</html>

源代码

动行结果