js更換圖片 - 台論之星

<html>
<body>
<script>
function changeImage()
{
element=document.getElementById('myimage')
if (element.src.match("bulbon"))
{
element.src="https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-ash3/q71/1069802_312367245565947_321647389_n.jpg";
}
else
{
element.src="https://fbcdn-profile-a.akamaihd.net/hprofile-ak-ash3/70338_100001712790855_899811106_q.jpg";
}
}
</script>

<img id="myimage" onclick="changeImage()" src="https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-ash3/q71/1069802_312367245565947_321647389_n.jpg">

<p>XXXXXX</p>

</body>
</html>

請問這樣寫哪裡錯了...........更換之後換不回來