<!DOCTYPE html>
<html>
<body>
<img id="img1" src="/i/ct_htmltree.gif">
<img id="img2" src="/i/dom_navigate.gif">
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML =
"第一幅图片的 id 是：" + document.images[0].id;
</script>
</body>
</html>