Queued.js

const RSVP = require('rsvp');

const Ember = { RSVP };

/**
 * Returns a promise and a trigger to start the job
 *
 * @export
 * @param {Function} func the job to execute
 * @param {any} scope the scope to bind the function to
 * @param {...any} args arguments 
 * @returns {array} [promise, job]
 */
function useDefer(func, scope, ...args) {
  const deferred = Ember.RSVP.defer();

  const trigger = async () => {
    try {
      const res = await func.apply(scope, args);
      deferred.resolve(res);
    } catch (e) {
      deferred.reject(e);
    }
  }

  return [deferred.promise, trigger]
}

/**
 * Returns a function that cannot run in parallel, any subsequent call will be queued
 *
 * @export
 * @param {function} func
 * @returns {function} a queued version of func
 */
function queued(func) {
  let queue = [];

  const next = async () => {
    if (queue.length) {
      await queue[0]();
      queue.shift();
      next();
    }
  };

  return function (...args) {
    const [promise, job] = useDefer(func, this, ...args);

    queue.push(job);

    if (queue.length === 1) {
      next(); // start
    }

    return promise;
  };
}



const waitFor = queued(async (time) => {
  return new Ember.RSVP.Promise((done) => {
    setTimeout(() => {
      console.log('done after ' + time + 'ms');
      done();
    }, time);
  });
});