<!DOCTYPE html>
<html>
<head>
<script>
function myFunction() {
document.getElementById("demo").innerHTML = "Hello World";
}
</script>
</head>
<body>
<p>单击按钮以触发函数。</p>
<button onclick="myFunction()">点击这里</button>
<p id="demo"></p>
</body>
</html>