What is a Higher Order Function in JavaScript ?

A higher-order function in JavaScript is a function that can accept other functions as arguments and/or return functions as results. In other words, it treats functions as first-class citizens. This feature allows for more flexible and powerful programming paradigms like functional programming.

Here's a basic example of a higher-order function:

function higherOrderFunction(func) {
    console.log("Inside the higher-order function");
    func(); // invoking the passed function
}

function someFunction() {
    console.log("Inside someFunction");
}

higherOrderFunction(someFunction); // passing someFunction as an argument

In the example above, higherOrderFunction is a higher-order function because it takes another function func as an argument and invokes it inside its body.

Higher-order functions are widely used in JavaScript, especially with concepts like callbacks, event handling, promises, and functional programming techniques like map, filter, and reduce. They promote code reusability and allow for cleaner, more concise code by abstracting common patterns into functions.