$('#overlay').css({
    width:  $(window).width(),
    height: $(window).height()
});

Lebar Mengikuti Ukuran Layar Saat Layar Berubah Ukuran

function elasticWidth() {
    $('#overlay').css({
        width:  $(window).width(),
        height: $(window).height()
    });
} elasticWidth();

$(window).resize(function() {
    elasticWidth();
});