Recursive async function

recursive-async.js

/**
 * Usage of async function you want to call recursively:
 *
 * 1. We're responsible for resolving our own promise in the recursive async func.
 * 2. We would like to execute other commands after the invoncation of the recursive func (line #32).
 *
 * Since we're creating a brand new promise in the function body, if we want to execute other code after the initial
 * recursive call, it's important to resolve the first promise when you want to exit the recursion. Otherwise, the code after 
 * the first call (line #32) won't be executed at all.
 */

async function sleep(ms) {
  return new Promise((r) => {
    setTimeout(r, ms);
  });
}

async function fakeFetch() {
  return new Promise(r => r({ fakeData: true }));
}

async function recursive(n, cb) {
  return new Promise(async r => {
    if (n < 3) {
      console.log('recur call.', n);
      await sleep(1000);
      await recursive(n + 1, cb || r);
      n = n + 1;
    } else {
      (cb && cb(666)) || r(666);
    }
  });
}

(async function () {
  const result = await recursive(0);
  console.log('done.', result);
}());