1. const asyncSequentializer = (() => {
    2.   const toPromise = (x) => {
    3.     if(x instanceof Promise) { // if promise just return it
    4.       return x;
    5.     }
    7.     if(typeof x === 'function') {
    8.       // if function is not async this will turn its result into a promise
    9.       // if it is async this will await for the result
    10.       return (async () => await x())();
    11.     }
    13.     return Promise.resolve(x)
    14.   }
    16.   return (list) => {
    17.     const results = [];
    19.     return list
    20.       .reduce((lastPromise, currentPromise) => {
    21.         return lastPromise.then(res => {
    22.           results.push(res); // collect the results
    23.           return toPromise(currentPromise);
    24.         });
    25.       }, toPromise(list.shift()))
    26.       // collect the final result and return the array of results as resolved promise
    27.       .then(res => Promise.resolve([...results, res]));
    28.   }
    29. })()