requestAnimationFrame无效

Question

所以我有这个代码，我想制作一个simlpe动画，但我似乎无法弄清楚它为什么不起作用。我只想通过改变圆的半径来玩动画。

function DrawCircle () {
     ctx.clearRect(0, 0, canvasHeight, canvasWidth);
     ctx.beginPath();
     this.y = 200;

     this.circle_radius = 150;

    //Create circle
    ctx.arc(200, this.y, this.circle_radius, 0, Math.PI * 2, false);
    ctx.fillStyle="#265D6D";
    ctx.fill();
    ctx.closePath();


};

var requestAnimationFrame = window.requestAnimationFrame || 
                            window.mozRequestAnimationFrame || 
                            window.webkitRequestAnimationFrame || 
                            window.msRequestAnimationFrame;

var test = new DrawCircle();


function moving(test) {

    test.circle_radius =+ 50;


    window.requestAnimationFrame(moving);


};
moving(test);