<script language="javascript">

    var x = 5.656;

    document.write(x.toFixed(0) + "<br/>"); // returns 6

    document.write(x.toFixed(2) + "<br/>"); // returns 5.66

    document.write(x.toFixed(4) + "<br/>"); // returns 5.6560

    document.write(x.toFixed(6) + "<br/>"); // returns 5.656000

</script>