Multitasking in JavaScript

When you start coding in JavaScript, a question often comes up: is it possible to perform several processes simultaneously (what is called multitasking in computing)? This would be useful if a process to be executed will take a long time, so as not to block other equally urgent processes.

JavaScript does not allow several processing operations to be carried out simultaneously. On the other hand, it is possible not to block the program (both on the client side in the browser, and on the server side with Node.js) by using the callback function (which we have already talked about when studying the forEach()method in the Accessing an element with the forEach(callback) method section).

Callback Function

A callback function corresponds to a processing function used as parameters of a JavaScript method or function. The callback function will be executed at the desired time by the method or function that uses it.

Node.js makes extensive use of this feature...