WWWForm in C#

Need to convert this into Javascript:

var url = "http://www.slimebass.com/test.php";
function Start() {
    var form = new WWWForm();
    form.AddField( "xp", Random.Range(0, 20));
    var download = new WWW( url, form );
    yield download;
    if(download.error) {
        print( "Error downloading: " + download.error );
        return;
    } else {
        Debug.Log(download.text);
    }
}

//SLIMEBASS

A few extra gotchas there I did not see on first read. Here is a untested conversion:

using UnityEngine;
using System.Collections;

public class Form : MonoBehaviour {
public string url = "http://www.slimebass.com/test.php";
    IEnumerator  Start (){
       WWWForm form = new WWWForm();
       form.AddField( "xp", Random.Range(0, 20));
       WWW download = new WWW( url, form );
       yield return download;
       if((!string.IsNullOrEmpty(download.error))) {
         print( "Error downloading: " + download.error );
       } else {
         Debug.Log(download.text);
       }
    }
}