Preload images

imagePreloader.js

const preloadImages = (images, callback) => {
  const loaded = [];
  const failed = [];

  const imageRequests = images.map(image => {
    const img = new Image();
    img.src = image;

    return new Promise((resolve) => {
      img.onload = () => {
        loaded.push(image);
        resolve();
      };

      img.onerror = () => {
        failed.push(image);
        resolve();
      };
    });
  });

  Promise
     .all(imageRequests)
     .then(() => callback(loaded, failed));
};