JSFiddle - React, Tailwind, and code Playground

JavaScript

var imgs = [
	'https://i.imgur.com/jUF6rcP.png',
  'https://i.imgur.com/4DJnFif.png',
  //'https://i.imgur.com/2MUX2qJ.jpg', // uncomment for early exit
  'https://i.imgur.com/yd6mjSY.png'
];

function reqListener () {
  var type = this.getResponseHeader('Content-Type');
  console.log('Checking:', type);
  if (type === 'image/png') {
  	var isComplete = nextImg();
    if (isComplete) {
  		console.log('ALL COMPLETE');
    }
  } else {
    console.log('EARLY EXIT');
  }
}

function nextImg () {
  var img = imgs.shift();
  if (img) {
		oReq.open("HEAD", img);
		oReq.send();
    return false;
  }
  return true;
}

var oReq = new XMLHttpRequest();
oReq.addEventListener("load", reqListener);
nextImg();