Asynchronous JavaScript

Working with AJAX (asynchronous JavaScript and XML) and the fetch API- used to make http requests to files, APIs and services (your own or external REST API)

Fetch is a newer standard.

Block and code- block until posts are fetched.

Asynchronous – pulls posts out of a synchronous function, but posts a call back, the do the next thing function does not have to wait- program will keep going.

Faster.

Most Async code will be part of an API or library:

· XMLHttpRequest and Fetch API

· External libraries: jQuery Ajax (bloated), Axios, or other HTTP libraries (Superagent)

· Node.js fs (filesystem)module, Node http

How to handle Async code:

· Callbacks

· Promises

· Async/Await

AJAX isn’t a language or a framework; it is a set of web technologies

· Sends and receive data from the client and server

· Done behind the scenes

· Don’t have to reload the web page

· XML has been replaced by JSON

· AJAX can alos work with plain text

· Fetches data

· Very interactive

· Can update little section of text without reloading web page

· AJAX call goes through an AJAX engine

· Uses XMLHttpRequest

· Parse and use data in application

· JS Call goes out from browser

· AJAX engine sends HTML response

· API has to have permissions granted

· COREs are enabled, and cross domain requests and made

· OAuth – used for authentication

· API in the form of an object

· Provided by the browsers javascript environment

· Methods transfer data between client and server

· Can be used with other protocols than http

· Can work with data other than XML (JSON, plain text)

· Fetch is part of Vanilla JS is what is recommended