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>
</head>		
<body>

<p id="p1">Hello World!</p>
<script id="myScript" src="demo_async.js.html" async></script>
<p>点击按钮检测是否异步执行脚本（一旦脚本可用）。</p>
<p id="demo"></p>
<button onclick="myFunction()">尝试一下</button>
<script>
function myFunction(){
	var x = document.getElementById("myScript").async;
	document.getElementById("demo").innerHTML = x;
};
</script>

</body>
</html>
源代码

动行结果
