iMichaelOwolabi

// Application logic that get employee records alongside their individual next of kin data in a non blocking format
const getAllEmployeeInformation = async () => {
  // Start recording the execution time of the following code.
  console.time('better await')
  const allEmployees = await getAllEmployees(); // Get all employee from the DB

  // Map individual employee record with their next of kin data and return the mapped data
  const employeeNextOfKinPromise = allEmployees.map(employee => {
    return getEmployeeNextOfKin(employee.id).then(nextOfKin => {
      return { ...employee, nextOfKin };

iMichaelOwolabi

// Application logic that get employee records alongside their individual next of kin data
const getAllEmployeeInformation = async () => {
  // Start recording the execution time of the following code.
  console.time('bad await')
  const allEmployees = await getAllEmployees(); // Get all employee from the DB

  const allEmployeeRecords = [];

  // Map individual employee record with their next of kin data and return the mapped data
  for (const employee of allEmployees) {

iMichaelOwolabi

/**
 * Dependent promise example
 */

// Employee records in the DB
const employee = [
  { id: 1, firstName: 'Ayo', lastName: 'Tunmise', dob: '1980-07-28' },
  { id: 2, firstName: 'Dayo', lastName: 'Owolabi', dob: '2000-03-08' },
  { id: 3, firstName: 'Michael', lastName: 'Ikechukwu', dob: '1997-01-31' },
  { id: 4, firstName: 'Hammed', lastName: 'Tukur', dob: '1900-08-07' },

iMichaelOwolabi

// Do this instead because unrelated awaits doesn't block each other ✅
const nonBlockinAsnycFunction = async () => {
  // Start recording the execution time of the following code.
  console.time('non-blocking-await');
  const promise1 = samplePromise1();
  const promise2 = samplePromise2();

  // Use promise.all to ensure the two promises are executed in parallel.
  const [promiseResult1, promiseResult2, promiseResult3] = await Promise.all([promise1, promise2, promise3]);

iMichaelOwolabi

// Do not do this since the awaits are not related in any way but are blocking ⛔️
const blockingAsnycFunction = async () => {
  // Start recording the execution time of the following code.
  console.time('blocking-await');
  const promiseResult1 = await samplePromise1();
  const promiseResult2 = await samplePromise2();

  console.log(promiseResult1);
  console.log(promiseResult2);

iMichaelOwolabi

/* Sample promises to simulate asynchronous operation.
* Let's assume these are sample DB operations and their equivalent response time
*
*/
const samplePromise1 = () => {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve('Promise 1 resolved after 2 seconds.');
    }, 2000);
  });

iMichaelOwolabi

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { GoogleStrategy } from './google.strategy'

@Module({
  imports: [],
  controllers: [AppController],
  providers: [AppService, GoogleStrategy],
})

iMichaelOwolabi

import { Injectable } from '@nestjs/common';

@Injectable()
export class AppService {
  googleLogin(req) {
    if (!req.user) {
      return 'No user from google'
    }

    return {

iMichaelOwolabi

import { Controller, Get, Req, UseGuards } from '@nestjs/common';
import { AppService } from './app.service';
import { AuthGuard } from '@nestjs/passport';

@Controller('google')
export class AppController {
  constructor(private readonly appService: AppService) {}

  @Get()
  @UseGuards(AuthGuard('google'))

iMichaelOwolabi

import { PassportStrategy } from '@nestjs/passport';
import { Strategy, VerifyCallback } from 'passport-google-oauth20';
import { config } from 'dotenv';

import { Injectable } from '@nestjs/common';

config();

@Injectable()
export class GoogleStrategy extends PassportStrategy(Strategy, 'google') {