2048 - random arrow play

2048-random.js

function fireKey()
{
    if(document.createEventObject)
    {
        var eventObj = document.createEventObject();
        eventObj.keyCode = Math.floor(Math.random() * (40 - 37 + 1)) + 37; 
        document.fireEvent("onkeydown", eventObj);   
    }else if(document.createEvent)
    {
        var eventObj = document.createEvent("Events");
        eventObj.initEvent("keydown", true, true);
        eventObj.which = Math.floor(Math.random() * (40 - 37 + 1)) + 37;
        document.dispatchEvent(eventObj);
    }
} 
setInterval(fireKey, 200);