rajatjain-21

async function getData() {
  // using await means the resolved value of the Promise is returned!
  const response = await fetch('https://blogger.ceo/api/blogs/image/random').then(
    (response) => response.json(),
  ); // .then still works when it makes sense!

  const otherResponse = await doOtherAsyncThing();

  // do stuff with `response` and `otherResponse`

rajatjain-21

// -------------------------------------------------------------------
// this function simulates a request that needs to run async
// -------------------------------------------------------------------
function doOtherAsyncThing() {
  return new Promise((resolve) => {
    setTimeout(() => resolve('it’s done!'), 500);
  });
}

rajatjain-21

// -------------------------------------------------------------------
// this function simulates a request that needs to run async
// -------------------------------------------------------------------
function favoriteBlogger(favorite) {
  return new Promise((resolve, reject) => {
    if (favorite === 'rajatexplains') {
      resolve(favorite);
    } else {
      reject('your preference is poor😛');

rajatjain-21

function PromisePolyfill(executor) {
  let onResolve, onReject;
  let fulfilled = false,
    rejected = false,
    called = false,
    value;

  function resolve(v) {
    fulfilled = true;
    value = v;

rajatjain-21

// This implementation does not work with Symbols, BigInts

function stringify(data) {
  if (data === undefined)
    return undefined
  if (data === null)
    return 'null'
  if (data.toString() === "NaN")
    return 'null'
  if (data === Infinity)

rajatjain-21

const input = [
  1, 2, 3,
   [4],
  [5, 6, [7], [8, [9, [10]]]],
  11, 12, 13,
  [14, [[[[[15, [16]]]]]]],
  17, 18,
  [19, [20, [21, [22, [23, [24, [[[[[25]]]]]]]]]]]
 ];
 

rajatjain-21

class MyPromise {
    static all(promises) {
    	let results = []; // to be resolved array of values
        let completedPromises = 0;
      	// return a promise
        return new Promise((resolve, reject) => {
          promises.forEach((promise, index) => {
            promise.then((value) => {
              results[index] = value;
              completedPromises += 1;

rajatjain-21

Function.prototype.bind = function(...args) {
  let obj = this;
  let params = args.slice(1);
  return function(...args2) {
    obj.apply(args[0], [...params, ...args2]);
  }
}

rajatjain-21

let obj = {
  a: 32,
  b: 34
}

Object.defineProperty(obj, Symbol.iterator, {
  configurable: false,
  enumerable: false,
  writable: false,
  value: function() {

rajatjain-21

function normalFunc(x,y,callback) {
  const result = x + y;
  callback(result);
}
async function run() {
  const promisedFn = promisify(normalFunc);
  const result = await promisedFn(4,3).then(data => data*data);
  console.log(result);
}
run()