Asynchronous calls allow client applications to react to changes on the server without impacting the users experience and without the need of the user to specifically interact with that interface to receive those updates.
It allows the system to process the results of a given request as soon as the information is received. It will not lock up the application during this period since the execution of this block of code is delayed.
Two ways to perform requests asynchronously in JavaScript are by using callbacks and by using promises. Note that these are both non-interchangeable, which means that you either use promises or callbacks, not both.
JavaScript promises vs callbacks, which is better? Let’s discuss.