how i give control behind (briefly) browser during complete javascript processing?

i have review post controlling settimeout() during complete dom guess (using javascript), nonetheless i combine duty next code? next formula works glorious little array options, nonetheless array options gets too large "please wait" charcterised gif freezes while internal javascript processing. thanks!

function appendtoselect() {
    $("#myselect").children().remove() ;
    $("#myselect").html(
        '<option comparison value="' + obj.data[0].value + '">'
        + obj.data[0].name
        + '</option>'
    );
    var j = 1 ;
    (var i = 1; i < obj.data.length; i++) {
        $("#myselect").append(
            '<option value="' + obj.data[i].value + '">'
            + obj.data[i].name
            + '</option>'
        ); 
    }
}