Change All The Hrefs On A Single Page

Ok so i'm trying to write a Greasemonkey script to change all the hrefs on a single page. The href by default looks like this:

<a href="javascript:get('246154895')" class="postid">ID</a>

What i'm trying to do is make the number from get() appear in stead of "ID". How should i get this done? I started up with this:

var posts = document.getElementsByClassname('postid');
for (i=0; i<posts.length; i++) {
//Replacing
}

But i doubt it will work, since there are other items with the class "postid" that aren't related to these tags i'm trying to change.