Javascript Random Generator to create custom URL variables

OK - I am trying to generate a custom URL with appended variables that are randomly generated.

Example: http://ift.tt/1NqhQ6R< location_id >&user=< user_name >&pass=< password >

I'm fine with all of the variable data being numeric, and have been trying to use this to generate the random numbers:

<p>Click the button to join.</p>

<button onclick="genID5()">Join</button>

<p id="generateID1"></p><p id="generateID2"></p><p id="generateID3"></p>

<script>
function genIDA() {
    var x = Math.floor((Math.random() * 1000000000000) + 101);
    document.getElementById("generateID1").innerHTML = x;
        console.log(x);
}

function genIDB() {
    var y = Math.floor((Math.random() * 1000000000000) + 101);
    document.getElementById("generateID2").innerHTML = y;
        console.log(y);
}

function genIDC() {
    var z = Math.floor((Math.random() * 1000000000000) + 101);
    document.getElementById("generateID3").innerHTML = z;
        console.log(z);
}

function genID5() {
    genIDA();
    genIDB();
    genIDC();

}


</script>

I am getting some nice big random numbers, and then I am trying to use this to append the URL:

function genURL() { 
        document.action = window.location.href = "http://ift.tt/1NqhQ6R + X + &user= y + &pass= + z; 
            return true; 
}

The URL function mostly works as far as pushing it to the Window object, and going to that URL - but getting the var values to insert is giving me a problem... I am not sure if it is because they are not nested, but I am getting undefined errors. Ultimately I dont need/want the user to see the numbers, and if the page loaded and executed to the script and the loaded the destination, that would be OK as well. I wanted to see the output difference between the HTML and the Console, and having the button to execute it helped me see the steps...

Any help would be appreciated! Thanks in advance!