Callback in JavaScript

A callback in JavaScript is a function that is passed as an argument to another function and is then invoked inside the outer function to complete some kind of routine or action. The primary purpose of a callback is to execute code in response to an event, which might be user-initiated, such as mouse clicks or typing. Callback functions are essential in JavaScript because many actions in JavaScript are asynchronous, meaning they execute in the background while the rest of the code runs. By using callbacks, developers can ensure that a function will not run before a task is completed but will run right after the task is completed, thus developing asynchronous JavaScript code and keeping it safe from errors.

There are two ways in which a callback may be called: synchronous and asynchronous. Synchronous callbacks are called immediately after the invocation of the outer function, with no intervening asynchronous tasks, while asynchronous callbacks are called at some point later, after an asynchronous operation has completed. Understanding whether the callback is synchronously or asynchronously called is particularly important when analyzing side effects.

In JavaScript, the way to create a callback function is to pass it as a parameter to another function and then call it back after the task is completed. Callback functions are widely used in event handling, asynchronous programming, and handling responses from APIs, among other use cases.

Overall, callbacks play a crucial role in JavaScript, enabling developers to write more efficient and responsive code by handling asynchronous operations and event-driven programming.

https://www.w3schools.com/js/js_callback.asp https://developer.mozilla.org/en-US/docs/Glossary/Callback_function https://www.simplilearn.com/tutorials/javascript-tutorial/callback-function-in-javascript