canvas draw grid (jquery + kaffeine)

gistfile1.txt

$.fn.grid = (interval) -> {
  var canvas = @[0], context = canvas.getContext('2d')
  x = y = 0.5
  while((x+=interval)<canvas.width) {
    context.moveTo(x,0)
    context.lineTo(x,canvas.height)
  }
  while((y+=interval)<canvas.height) {
    context.moveTo(0,y)
    context.lineTo(canvas.width,y)
  }
  context.strokeStyle = "rgba(0,0,0,0.5)"
  context.stroke();
}

// $("canvas").grid(16)