let draw =
  () {
    case Dom.Canvas.fromDomElement(canvas) {
      Maybe::Just(el) =>
        {
          // Add five color stops
          let gradient =
            Canvas.createConicGradient(el, 0, 100, 100)
            |> CanvasGradient.addColorStop(0, "red")
            |> CanvasGradient.addColorStop(0.25, "orange")
            |> CanvasGradient.addColorStop(0.5, "yellow")
            |> CanvasGradient.addColorStop(0.75, "green")
            |> CanvasGradient.addColorStop(1, "blue")
          // Set the fill style and draw a rectangle
          el
          |> Canvas.setFillStyle(CanvasFillStyle::Gradient(gradient))
          |> Canvas.fillRect(20, 20, 200, 200)
          ""
        }
      Maybe::Nothing =>
        ""
    }
  }
{
  await Timer.timeout(0)
  draw()
}
<canvas as canvas
  width="240"
  height="240"/>