let draw =
  () {
    case Dom.Canvas.fromDomElement(canvas) {
      Maybe::Just(el) =>
        {
          el
          |> Canvas.setLineDash([4, 16])
          // Dashed line with no offset
          el
          |> Canvas.beginPath()
          |> Canvas.moveTo(0, 50)
          |> Canvas.lineTo(300, 50)
          |> Canvas.stroke()
          // Dashed line with offset of 4
          el
          |> Canvas.beginPath()
          |> Canvas.setStrokeStyle(CanvasFillStyle::String("red"))
          |> Canvas.setLineDashOffset(4)
          |> Canvas.moveTo(0, 100)
          |> Canvas.lineTo(300, 100)
          |> Canvas.stroke()
          ""
        }
      Maybe::Nothing =>
        ""
    }
  }
{
  await Timer.timeout(0)
  draw()
}
<canvas as canvas/>