Load Images in JS, do something when loaded

load_images.js

function loadImage(url) {
  return new Promise((resolve, reject) => {
    let img = new Image();
    img.addEventListener('load', e => resolve(img));
    img.addEventListener('error', () => {
      reject(new Error(`Failed to load image's URL: ${url}`));
    });
    img.src = url;
  });
}

async function go() {
// load the image, and append it to the element id="image-holder"
img = await loadImage('http://thecatapi.com/api/images/get?format=src&type=jpg&size=small')
document.getElementById('image-holder').appendChild(img)

}

go()
  
/*  loadImage('http://thecatapi.com/api/images/get?format=src&type=jpg&size=small')
    .then(img => document.getElementById('image-holder').appendChild(img))
    .catch(error => console.error(error)); */