JSFiddle - React, Tailwind, and code Playground

HTML

<div id="imageContainer"></div>
<div id="overlay"></div>

CSS

#overlay {
 height:100px;
 width: 100px;
 background-color: red;    
}

JavaScript

var amountOfImagesLoaded = 0;

var img1 = new Image(),
    img2 = new Image(),
    img3 = new Image();

img1.src = "http://upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Chihuahua_puppy_001.jpg/220px-Chihuahua_puppy_001.jpg";
img2.src = "http://www.pupmart.co.uk/wp-content/uploads/2011/10/puppies-rehoming.jpg";
img3.src = "http://www.makems.com/graphic/puppies-2.jpg";

var imageContainer = document.getElementById("imageContainer");

//This setTimeout it's only here so you can get a glimpse of what is happening, in your real application you wouldn't use it
setTimeout(function() {
    imageContainer.appendChild(img1);
    imageContainer.appendChild(img2);
    imageContainer.appendChild(img3);
}, 800);

var imageOnLoadFunction = function(){
    amountOfImagesLoaded++;
    if(amountOfImagesLoaded === 3) {
     jQuery("#overlay").fadeOut();   
    }
};


img1.onload = img2.onload = img3.onload = imageOnLoadFunction;