Higher-order functions, Callback Functions, and Closures in JavaScript

We’ll look at the HOF (Higher-order function), Callbacks, and the wacky JavaScript Closures in this post, which have all made us pull our hair out at some point throughout our learning path.

1. Higher-Order Functions(HOF)

Functions can be assigned to variables in Javascript in the same manner that strings, numbers, booleans, and arrays can. They can be supplied as arguments to other functions or returned from them.

A function that accepts functions as parameters and/or returns a function is referred to as a “higher-order function.”

For example

const isEven = (x) => x > 0 && x % 2 === 0
const logger = (Fn, Num) => {
  const isEven = Fn(Num)
  console.log(isEven)
}
logger(isEven, 6)

Because it accepts the isEven function as an input, “logger” is the Higher-Order Function in the preceding excerpt.

Some JavaScript methods like map, filter, reduce, etc are higher-order functions.

2. Callback Function