let draw =
  () {
    case Dom.Canvas.fromDomElement(canvas) {
      Maybe::Just(el) =>
        {
          // Save the current state
          el
          |> Canvas.save()
          // Set the fill style and draw a rect
          el
          |> Canvas.setFillStyle(CanvasFillStyle::String("green"))
          |> Canvas.fillRect(10, 10, 100, 100)
          // Restore to the state saved by the most recent call to save()
          el
          |> Canvas.restore()
          |> Canvas.fillRect(150, 40, 100, 100)
          ""
        }
      Maybe::Nothing =>
        ""
    }
  }
{
  await Timer.timeout(0)
  draw()
}
<canvas as canvas/>