What is Asynchronous Programming

Synchronous Code

posts = loadPostsSync();
// ... wait till posts are fetched
// ... do something with posts

doTheNextThing(); // Has to wait until posts load

Asynchronous Code

posts = loadPostsAsync(function(){
    // ... wait till posts are fetched
    // ... do something with posts
});

doTheNextThing(); // Doesn't have to wait until posts load

Most Async code You work with will be part of an API or library

  • XMLHTtpRequest & Fetch
  • jQuery Ajax, Axios, other HTTP libraries
  • Node.js fs ( filesystem ) module

There are few ways to work with Async code

  • Callbacks
  • Promises
  • Async / Await

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