I'm trying to draw a circle in the canvas in javascript but it's not working and I'm not getting an error. I've done it before and it usually works, but for some reason now it isn't. Any help would be highly appreciated.

// VARIABLES
var x = 100 ;
var y = 100;
var r = 50;
var c = 272;
var a = 0.9;

// EXECUTABLE CODE
circle();

// FUNCTION
function circle(x,y,r,c,a){
    ctx.beginPath();
    ctx.arc(x,y,r,0,Math.PI*2);
    ctx.fillStyle = "hsl("+c+", 100%, 50%,"+a+")";
    ctx.fill();
}