版权声明： https://blog.csdn.net/eds124/article/details/84111584
<!DOCTYPE html>
<html>
<head>
<script>
function displayDate()
{
document.getElementById("demo").innerHTML=Date();
}
document.write("<h1>这是一个标题</h1>");
document.write("<p>这是一个段落。</p>");
</script>
</head>
<body>
<p id="demo">id="demo"里面的demo必须跟document.getElementById("demo")里的demo一致</p>
<button type="button" onclick="displayDate()">显示日期(onclick="displayDate()"里面的displayDate()必须跟function里面的displayDate()一致)</button>
</body>
</html>