Async JavaScript basics: Promises and async/await

async-javascript-basics.js

// @ts-nocheck
/* eslint-disable */

// Asynchronous JavaScript basics

// Contrary of Synchronous
// Synchronous code runs line by line, instantly: eg

function logSum(a, b) {
  console.log(a + b)
}

logSum(1, 2)
logSum(2, 2)
logSum(3, 2)
logSum(4, 2)


// Why do we use async?
// Calling other services: eg:
// Get data from another website or API
// Retrieving / storing data in a database
// Write / Read files from file system

// Example
// Definition of the API used in this example: https://github.com/lukePeavey/quotable

// Get a list of authors
const listAuthorsUrl = 'http://api.quotable.io/authorsblabla'

// Get a random quote of the first author in the list
const authorRandomQuoteUrl = (author) => {
  return `https://api.quotable.io/random?author=${author}`
}

const axios = require('axios')

// The promise way (The old way)
// You have to chain them if you need to use
// multiple promises that depend on each other
axios
  .get(listAuthorsUrl)
  .then((response) => {
    const firstAuthorSlug = response.data.results[0].slug
    return firstAuthorSlug
  })
  .then((firstAuthorSlug) => {
    return axios.get(authorRandomQuoteUrl(firstAuthorSlug))
  })
  .then((response) => {
    console.log(response.data)
  })
  .catch((error) => {
    console.log('I CAUGHT AN ERROR', error)
  })


// The async/await way (The modern way)
// The async modifier is added to the function declaration
// The await modifier is added before asynchronous function calls
async function getRandomQuoteFromFirstAuthorInTheList() {
  try {
    const authorListResponse = await axios.get(listAuthorsUrl)
    const firstAuthorSlug = authorListResponse.data.results[0].slug

    const randomQuoteFromAuthor = authorRandomQuoteUrl(firstAuthorSlug)
    const randomQuoteResponse = await axios.get(randomQuoteFromAuthor)
    const quote = randomQuoteResponse.data

    console.log(quote)
  } catch (error) {
    console.log('CAUGHT YA', error)
  }
}

getRandomQuoteFromFirstAuthorInTheList()