java Scripts :: associated array in Javascripts

<script>

//for in loop only used associated array

var x;

var person={Rollno:111, fname:"payal",lname:"joshi"};

    for (x in person)
    {

        document.write(person[x] + " ");
    }

        document.write("<br><br><br>");
        document.write(person['Rollno']+"<br>");
        document.write(person['fname']+"<br>");
        document.write(person['lname']+"<br>");
        var a={a:10,b:20,c:30,d:40};
        var x1;

for(x1 in a)
{

    document.write("<br>"+a[x1]);
}



</script>