<!DOCTYPE html>
<html>
<head>
<script>
function lighton()
{
document.getElementById('myimage').src="/img/eg_bulbon.gif";
}
function lightoff()
document.getElementById('myimage').src="/img/eg_bulboff.gif";
</script>
</head>
<body>
<img id="myimage" onmousedown="lighton()" onmouseup="lightoff()" src="/img/eg_bulboff.gif" />
<p>按住鼠标不放可以点亮这盏灯！</p>
</body>
</html>