fetch examples:

progress-helper-usage.js

// The progressHelper could be inline w/ .then() below...
const streamProcessor = progressHelper(console.log)

fetch('https://fetch-progress.anthum.com/20kbps/images/sunrise-progressive.jpg')
  .then(streamProcessor) // note: NO parentheses because `.then` needs to get a function
  .then(response => response.blob())
  .then(blobData => {
    // ... set as base64 on an <img src="base64...">
  })