let start = {x: 100, y: 100};
let controlPoint1 = {x: 100, y: 200};
let controlPoint2 = {x: 200, y: 200};
let endPoint = {x: 200, y: 100};

ctx.moveTo(start.x, start.y); //Move to start point
ctx.bezierCurveTo(
  controlPoint1.x, controlPoint1.y,
  controlPoint2.x, controlPoint2.y,
  endPoint.x, endPoint.y
); //Draw curve
ctx.stroke(); //Draw outline