Process all requests guaranteeing synchronous execution (e.g. 1 then 2 then 3)

synchronous-execution.js

function asyncFunction (item, cb) {
  setTimeout(() => {
    console.log('done with', item);
    cb();
  }, 100);
}

let requests = [1, 2, 3].reduce((promiseChain, item) => {
    return promiseChain.then(() => new Promise((resolve) => {
      asyncFunction(item, resolve);
    }));
}, Promise.resolve());

requests.then(() => console.log('done'))