Promises

Should I read this?

If you’re a JavaScript developer who still uses callbacks (on either the client side or server side) then this post is for you. If you don’t know what Promises are, then you probably will find it useful.

Back in time, JavaScript was initially built to add interactivity to web pages and to be used on the client side. It has been designed to handle user interactions using events and event handlers. Also to make communications with the server. All of these stuff are Asynchronous operations. we can say:

JavaScript is an event-driven programming language.

which means, the flow of the program is determined by events such as user actions (mouse clicks, key presses) or messages from other programs/threads.

So?

So, JavaScript is designed over and encourages the usage of callbacks.

Here’s a simple illustration of how a callback way works. #Main script wants to execute #Function_B after