Wait for all images

index.js

const images = ['http://picsum.photos/300/300?r&a=1', 'http://picsum.photos/300/300?r&a=2', 'http://picsum.photos/300/300?r&a=3']

const imageLoadPromise = (src) => new Promise((resolve, reject) => {
  const img = new Image()

  img.onload = resolve
  img.src = src
})

Promise.all(images.map(imageLoadPromise))
  .then(() => console.log('all done'))