ctx.beginPath();
/* ctx.arc(x, y, radius, startAngle, endAngle[, counterclockwise] */
ctx.arc(20, 50, 10, 0, 2*Math.PI)
ctx.stroke();
// or ctx.fill();
<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Draw a circle</title>
</head>
<body onload="draw();">
<canvas id="circle" width="150" height="150"></canvas>
</body>
</html>
ellipse(x,y,x,y); //x and y represnt number value not string