Canvas context.toDataUrl() returning a "data:"

Question

I'm trying to create a function that converts an image url to a base64 string. The problem is that the return value of the toDataUrl function is "data:"

`export const getBase64FromImageUrl = (url: string): string => {
  const img = new Image()
  img.src = url
  img.crossOrigin = 'anonymous'

  const canvas = document.createElement('canvas')
  canvas.width = img.width
  canvas.height = img.height
  const ctx = canvas.getContext('2d')

  if (!ctx) return ''

  ctx.drawImage(img, 0, 0)
  return canvas.toDataURL()
}`

and then I call this function passing a url from a jpg image store in a s3 bucket. The bucket allows cross origin so I think that's not the problem.