A simple async mutex implementation

script.js

let locks = [];
const fn = async () => {
  let resolve;
  locks.push(new Promise(r => (resolve=r)));
  let lock;
  while (locks.length > 1 && (lock = locks.shift()))
    await lock;

  console.log(new Date());
  setTimeout(resolve, 1000);
}
Promise.all((Array.from(Array(10), fn))).then(() => console.log('Done.'));