Chrome和IE-刷新用户界面

Question

I have a jquery function which call two web services with $.ajax

$.ajax({
    url: url1,
    success: function (datas) {
        $("#elt-1").text($(datas).size());
        for(var index = 0 ; index < $(datas).size() ; index++) {
            $.ajax({
                url: url2,
                async: false,
                success: function (data) {
                    console.info("Data [" + data + "] OK");
                    $("#elt-2").text(index + 1);
                    var progres = (index + 1) * 100 / $(datas).size();
                    $("#j-progress-bar").val(progres);
                }
            });
        }
    }
});

The instruction console works on any browser but instructions text work well only on firefox. On chrome and IE, UI is refresh only at the end of the function.

If I put an alert instruction after the set val of $("#j-progress-bar"), UI is correctly refresh.

What is the solution to update UI in real time ?

Thanks for your help.