JS Canvas Game Prototype

<script>
var fps = 30;
var time = 0;
var deltaTime = 1;

function Start() {
	looper();
}

function looper() {
    setTimeout(function() {
        requestAnimationFrame(looper);

        // Calculate the deltaTime
        var now = new Date().getTime();
        deltaTime = 1 / (now - (time || now));
        time = now;

        // Your code here
        mainLoop();
    }, 1000 / fps);
}

function mainLoop()
{
	console.log("deltaTime = " + deltaTime);
}

Start();
</script>