fetch('https://upload.wikimedia.org/wikipedia/commons/7/77/Delete_key1.jpg')
.then(res => res.blob()) // Gets the response and returns it as a blob
.then(blob => {
// Here's where you get access to the blob
// And you can use it for whatever you want
// Like calling ref().put(blob)
// Here, I use it to make an image appear on the page
let objectURL = URL.createObjectURL(blob);
let myImage = new Image();
myImage.src = objectURL;
document.getElementById('myImg').appendChild(myImage)
});