const imageURL = "https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSw0gWlEimLsPylCKAm95y1K27fCdzXEHGhXYTfEWXo&s"

function blob2Base64(blob) {
  const reader = new FileReader();
  reader.readAsDataURL(blob);

  return new Promise((resolve) => {
    reader.onloadend = () => {
      resolve(reader.result)
    };
  })
}

fetch(imageURL).then((res) => {
  return res.blob()
}).then(async (blob) => {
  document.querySelector("#img").src = await blob2Base64(blob)
})