constructor Qew(maxConcurrency: number = 1, delay: number | (() => number) = 0): Qew;

const Qew = require("qew");

const qew = new Qew(); // maxConcurrency of 1, delay of 0ms
const qew = new Qew(3); // maxConcurrency of 3, delay of 0ms
const qew = new Qew(2, 250); // maxConcurrency of 2, delay of 250ms between end and start of functions

const getRandomDelay = () => Math.random() * 1000;

const qew = new Qew(2, getRandomDelay);
// maxConcurrency of 2, delay will be a new random value between 0ms and 1000ms

Qew.push(asyncFunc: () => Promise<T>): Promise<T>;

// returns a promise, that runs when it is its turn in the queue.
// will resolve or reject depending on asyncFunc's resolution
const prom = qew.push(asyncFunc);

prom
    .then(result => ...)
    .catch(error => ...);

// `push`'s result can also be `await`ed in an async function like any promise
const doStuff = async () => {
    const result = await qew.push(asyncFunc);
    // do something  with `result`
}

const qew = new Qew(1, 100); // for API that has a rate limit of 10 reqs/sec

qew.push(() => accessApi("a")).then(callback);
qew.push(() => accessApi("b")).then(callback);
qew.push(() => accessApi("c")).then(callback);

function callback(err, result) {
  if (err) {
    return console.error(err);
  }
  console.log(result);
}

constructor Qew(maxConcurrent: number = 1, delay: number | (() => number) = 0): Qew;

Qew.push(asyncFunc: () => Promise<T>): Promise<T>;