keydown, keyup, keypress

HTML

<span id="state-msg"></span>

JavaScript

var down = [];
var msg = document.getElementById('state-msg');
document.body.addEventListener('keydown', function(e) {
		e.stopPropagation();  e.preventDefault();
    var key = e.code;
		if(down.indexOf(key)==-1) down.push(key);
    msg.textContent = JSON.stringify(down);
});

document.body.addEventListener('keyup', function(e) {
		e.stopPropagation();  e.preventDefault();
     var key = e.code;
		down.splice(down.indexOf(key),1);
    msg.textContent = JSON.stringify(down);
});