Example of how async JavaScript works with promises

faux_apis.js

const getRandomTimeOutInMs = () => Math.floor(Math.random() * 5000);

const apis = ["Facebook", "Twitter", "Instagram"];

const start = () => {
  apis.forEach(api => {
    let currentApi = new Promise(function(resolve, reject) {
      let timeout = getRandomTimeOutInMs();
      setTimeout(() => {
        resolve(`The ${api} API took ${timeout} ms to respond.`);
      }, timeout);
    });
    currentApi.then(result => {
      console.log(result);
    });
  });
};

document.addEventListener("DOMContentLoaded", start);

More info on promises: https://javascript.info/promise-basics