Changing the data in URL strings - Using API for database requests

Using an API I am creating a forum using Javascript.

When a user clicks on the thread title on the index.html page they are taken to a page called thread.html on here I am using an API call to display the results for the thread with ID 1

var threadRequest = new Request.JSON({
  url: 'control.php?action=getThread&id=1',
  onSuccess: threadSuccess
    }).send();

My question is how would I change this so it knows which thread has been clicked so it knows which thread to call, I have tried

function callThread(thread){
  var threadRequest = new Request.JSON({
    url: 'control.php?action=getThread&id='+thread,
    onSuccess: threadSuccess
     }).send();
}

with thread being the foreign key in the table linked to the API.

The thread titles are displayed like so

var jsonRequest = new Request.JSON({
    url: 'control.php?action=getThreadList',
    onSuccess: ajaxSuccess

}).send();

This is the threadSuccess function as well

function threadSuccess (jArray){
    jArray.each(function(post){
        var postObject = new PostItem(post.id, post.name, post.comment, post.thread);
        postObject.display().inject($('postList'));
    })
}

My question is do you get it so that the url string would do something like url: 'control.php?action=getThread&id=what ever number thread the user has clicked on

The post table contains the fields id, name, comment, timestamp and thread (this will define which thread the post will be in.)

and a thread table contains id and title.