1，改变 HTML 输出流
<script>
document.write(Date());
</script>
2，改变 HTML 内容
<script>
document.getElementById("p1").innerHTML="New text!";
</script>
3，改变thml属性
<!DOCTYPE html>
<html>
<body>
<img id="image" src="smiley.gif">
<script>
document.getElementById("image").src="landscape.jpg";
</script>
</body>
</html>