Get Attribute Date in DIV [closed]

At certain div I make an area calculation for a responsive site.

<div id="iframe-game" class="help" data-scale="0.8264794383149449">
</div>

By jQuery I try to get the value of the attribute data-scale like this:

$("#iframe-game").data('scale');
$("#iframe-game").attr('data-scale');
$("#iframe-game").prop('data-scale');

I have tried these three ways. But it does not. And when I enter the Inspect Element, it's there in the% s like% paste up there.

I do this in div :

$(window).load(function(){
    setTimeout(function(){
       var percent = $('div#iframe-game').attr('data-scale');
    },1);
});

I use version 1.11 of jQuery.

What I believe is happening is that the value has not been set yet and onLoad is being faster to load ... and so it gets a null value.

How do I set onLoad :

$('#iframe-game-box').each(function(){

    var iframe = $(this);
    $(window).on('load resize',setViewport);

    function setViewport(){

            var iframeGame = iframe.contents().find("#iframe-game");
            var iframeHeight = iframe.contents().find('body')[0].scrollHeight;
            var iframeWidth = iframeGame.width();
            var windowHeight = $(window).height();
            var windowWidth = $(window).width();

            //Verifica se vai adicionar um valor ao gap
            var heightGap = 0;
            if(iframeHeight > windowHeight){
                heightGap = 70;
            }

            //Verifica se fará a nova escola de acordo com a altura ou largunra
            if(windowWidth > windowHeight){
                var newScale = ((windowHeight - heightGap) * 100 / iframeHeight) / 100;
            }else if(windowHeight > windowWidth){
                var newScale = (windowWidth * 100 / iframeWidth) / 100;
            }

            if(newScale > 1){ newScale = 1; }

            iframeGame.css({
                '-webkit-transform' : 'scale(' + newScale + ')',
                '-moz-transform'    : 'scale(' + newScale + ')',
                '-ms-transform'     : 'scale(' + newScale + ')',
                '-o-transform'      : 'scale(' + newScale + ')',
                'transform'         : 'scale(' + newScale + ')'
            }).attr('data-scale', newScale);
    });
});