代码示例:(标识:eg_js_function_1)
<!DOCTYPE html>
<html>
<head>
<script>
function myFunction() {
  document.getElementById("demo").innerHTML = "Hello World!";
}
</script>
</head>

<body>

<p>单击“试一试”时,将调用一个函数。</p>

<p>该功能将显示一条消息。</p>

<button onclick="myFunction()">试一试</button>

<p id="demo"></p>

</body>
</html>
运行结果: