Learn how to create a callback function in JavaScript and use it for various purposes, such as asynchronous programming, modularity, flexibility, and custom events.

Those are examples of higher-order functions that accept functions as arguments, but plenty of them return functions as well. If you’ve ever seen a function call that has two sets of parentheses ...

In JavaScript, though, the same code is perfectly fine: This is because JavaScript scopes your variables to functions and not to if-blocks. But, we can achieve block-like scope through the use of ...