Круговой таймер в canvas

 var myCanvas = document.getElementById("myCanvas"),
    context = myCanvas.getContext("2d"),
    timeLimit = 15E3,
    timeStart = (new Date).getTime(),
    canvasSize = 24,
    lineWidth = 3,
    drawX = drawY = radius = canvasSize / 2;
    radius -= lineWidth / 2;
    myCanvas.width = canvasSize;
    myCanvas.height = canvasSize;
 
function go() {
    context.beginPath();
    context.lineWidth = lineWidth;
    context.lineCap = "round";
    context.strokeStyle = "rgb(251 134 125)";
    var a = ((new Date).getTime() - timeStart) / timeLimit;
  console.log((new Date).getTime())
  console.log(a)
    context.clearRect(0, 0, canvasSize, canvasSize);
    context.font = '8px "Tahoma"';
    context.color = "rgb(251 134 125)";
    context.fillText((4 - a*4)|0, radius, drawY);
    context.arc(drawX, drawY, radius, -Math.PI / 2 + 2 * Math.PI * a, -Math.PI / 2, !1);
    context.stroke();
    1 < a && (timeStart = (new Date).getTime());
    timer = window.setTimeout(go, 50)
}
go();