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

// 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

// 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

/**
 * 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

// 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

// 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

/**
 * Event loop blocking code sample
 */
const fs = require('fs');

const countries = fs.readFileSync('countries.csv');
console.log(countries.toString());

// Other JavaScript code below this line will be blocked until the file reading completes.
console.log('Other JAVASCRIPT THAT IS BLOCKED');

iMichaelOwolabi

// A better way of reading file that doesn't block the event loop
const fs = require('fs');
  fs.readFile('countries.csv', (error, data) => {
    if (error) {
      throw new Error(error);
    }
    console.log(data.toString());
  });

// Other JavaScript code below this line will not be blocked which is good.

iMichaelOwolabi

import express from 'express';
import { config } from 'dotenv';

config();

const app = express();

app.use(express.json());
const port = process.env.PORT ?? 3000;

iMichaelOwolabi

import { config } from 'dotenv';
import { Client } from 'redis-om';

config();

const redisCloudConnectionString = `redis://${process.env.REDIS_DB_USER}:${process.env.REDIS_DB_PASS}@${process.env.REDIS_DB_URL}`;

const redisClient = new Client();

await redisClient.open(redisCloudConnectionString);