Canvas에서 오각형을 쓰다

createStar("test",150,100,50,"yellow");

function createStar(selector,x,y,r,color){
    //五芒星の時の角度
    var c1 = createCordinate(r,-90);
    var c2 = createCordinate(r,-234);
    var c3 = createCordinate(r,-18);
    var c4 = createCordinate(r,-162);
    var c5 = createCordinate(r,-306);

    var canvas = document.getElementById(selector);

    if(canvas == null){
        canvas = document.getElementsByClassName(selector)
    }

    var context = canvas.getContext('2d');
    context.fillStyle = color;
    context.lineWidth = 0;

    context.beginPath();
    context.moveTo(x,y-r);
    context.lineTo(c1.x + x, c1.y + y);
    context.lineTo(c2.x + x, c2.y + y);
    context.lineTo(c3.x + x, c3.y + y);
    context.lineTo(c4.x + x, c4.y + y);
    context.lineTo(c5.x + x, c5.y + y);
    context.closePath();

    context.fill();
    //context.stroke();

    function createCordinate(r,angle){
        var x = r * Math.cos(angle / 180 * Math.PI);
        var y = r * Math.sin(angle / 180 * Math.PI);

        return {
            "x" : x,
            "y" : y
        };
    }
}