void init()
{
    lastSecond = window.performance.now();
    window.requestAnimationFrame(draw);
}

void draw() {

    gl.clearColor(0.8, 0.8, 0.8, 1);
    gl.clearDepth(1.0);
    gl.clear(COLOR_BUFFER_BIT | DEPTH_BUFFER_BIT);

    frameCounter++;
    double timeNow = window.performance.now();

    if (timeNow > lastSecond + 1000)
    {
      e.text = ((frameCounter * 1000) / ((timeNow - lastSecond))).toStringAsFixed(2);
      lastSecond = window.performance.now();

      frameCounter = 0;
    }

    window.requestAnimationFrame(draw);
}