async function populate() {

  const requestURL = 'https://mdn.github.io/learning-area/javascript/oojs/json/superheroes.json';
  const request = new Request(requestURL);

  const response = await fetch(request);
  const superHeroes = await response.json();

  populateHeader(superHeroes);
  populateHeroes(superHeroes);

}