代码示例:(标识:eg_js_dom_getelementbyid)
<!DOCTYPE html>
<html>
<body>

<h1>通过 id 查找 HTML 元素</h1>

<p id="intro">Hello World!</p>

<p>本例演示 <b>getElementsById</b> 方法。</p>

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

<script>
var myElement = document.getElementById("intro");
document.getElementById("demo").innerHTML = 
"来自 intro 段落的文本是:" + myElement.innerHTML;
</script>

</body>
</html>
运行结果: