I need to create dynamic global two dimensional array in jquery or javascript

My function is like this

<script>
var index = 0;
var globalArray = new Array();

function createArray(){

    var loop = globalArray[index].length;
    var name = $.("#uname").val();

    if(loop == 0){
     globalArray[index][0] = uname;
    }else{
      globalArray[index][loop++] = uname;
    }

}

</script>

<div><input type="text" id="uname"> <input type='button' value='save' onclick='createArray();'> </div>

On click of that button I am getting this error "globalArray[index] is undefined"

How can I create one global array using jquery or javascript like this.

I dont want any hidden field and all.

Please help me.

Thanks