Simple Utility to resolve an array of promises in series.

resolve_util.js

function promiseReducer(arrayOfPromiseHolders, resolve, reject) {
  if (arrayOfPromiseHolders.length > 0) {
    const promiseHolder = arrayOfPromiseHolders.shift();
    promiseHolder().then(() => {
      promiseReducer(arrayOfPromiseHolders, resolve, reject);
    }).catch((err) => {
      reject(err);
    });
  } else {
    resolve();
  }
}

/**
* Resolve in series takes an array of functions that return a promise, and then
* resolves them in series
* 
* Usage:
* resolveInSeries([
*   () => {
*     return new Promise((resolve) => { console.log("I will print first!"); resolve(); })
*   },
*   () => {
*     return new Promise((resolve) => { console.log("I will print second!"); resolve(); })
*   }
* ]).then(() =>  {
*   console.log("I will print at the end");
* });
*/
function resolveInSeries(arrayOfPromiseHolders) {
  return new Promise((resolve, reject) => {
    promiseReducer(arrayOfPromiseHolders, resolve, reject);
  });
}

export resolveInSeries;