FileReader Constraints Functions - on<events>

Hello guys,

i create simple function where from selected files via input file element, by using FileReader I create simple image element. Its working fine but inside of this function during using class FileReader which contains Constraints Function (onloadstart, onprogress, onload, onabort, onerror, onloadend - i am not sure but I called them as Constraints Function) I cant find solution in Haxe how to do for example this steps: if onloadstart is finished, then onload and then onloadend. I know that there are Promises like one solution (i am not sure if there is more practically solutions) but I dont know how to do it in Haxe.

If you have any solutions i am using the newest version of Haxe and also I can try it on 3.4.7

This is my function but as i mentioned above Constraints are wrong inside of function,

Thanks you a lot of

private function createImageFromFileViaFileReader( file:File ):ImageElement
        var img:ImageElement = cast document.createElement("img");
        var fileReader = new FileReader();

        // TO DO
        fileReader.onloadstart = function(e) {
            if(window.confirm()) {
                 fileReader.onload = function(e) {
                     img.src =;
                     img.height = 60;

                 fileReader.onloadend = function(e) {

                return true;

            } else {
                return false;



        return img;