Hy, a bit late but i made a workaround :

I provide here the Javacode, the needed html been explained on the top.

// This Code needs a InputField with ID "Sequenz"
//  -  a div with ID "Feedback" to show keydown char
//  -  a div with ID "FeedbackU" to show input char
//  -  a div with ID "key" to show entered key 

function init(){
    document.addEventListener('keydown', function(event){keydown(event);})
    document.getElementById('Java').innerHTML="Keyress";

    //Use this Line to add Events to every Input Field, just call with the ID - Number
    AddEventtoInput("Sequenz");
}

var handled = false;
function keydown(event){    
    if(event.which == 229){
        return;
    }else{
        handled = true;
        document.getElementById('Feedback').innerHTML = event.key;
        if (keypress(event.key) == true){
            event.preventDefault();
        }
    }

    // ----- Demonstration of values. Please Delete.
    document.getElementById('Feedback').innerHTML = document.getElementById('Feedback').innerHTML + " - " + event.which;
    // ------------------------
}
function AddEventtoInput(div){
    document.getElementById(div).addEventListener("input", keyinput);
}
function keyinput(event){
    var key = event.target.value;
    key = key.slice(-1);
    if(key.indexOf('\t') != -1){key = "Tab";}
    if(handled == false){

        // ----- Demonstration of values. Please Delete.
        document.getElementById('FeedbackU').innerHTML = key;
        // ------------------------

        if (keypress(key) == true){
            event.target.value = event.target.value.slice(0,-1);
        }

    }else{
        handled = false;
    }
}
function keypress(key){
    prevent = false;
    //------------------------ Here Code to Check entered Char, Change prevent to true to prevent Char
    document.getElementById('key').innerHTML = key;
    //-----------------------
    return prevent;
}

I have written this code and it is free of use (Public Domain). Please help yourself to add it in your project.

M. Glaser

Munich Germany