High-order functions are a fundamental concept in functional programming, and are widely used in JavaScript. These functions take one or more functions as arguments, and/or return a function as its result. In this article, we will explore what high-order functions are, why they are useful, and provide examples of how to use them in JavaScript.
What are Higher-order functions?
First, let’s define what a high-order function is. A high-order function is a function that takes one or more functions as arguments, and/or returns a function as its result. These types of functions are powerful tools in functional programming and are commonly used in JavaScript. High-order functions are used to compose complex behaviors from simple functions and can help to improve the readability and maintainability of code.
One of the main benefits of high-order functions is that they allow for code reuse. By passing a function as an argument to another function, we can use the same function in multiple places, without having to copy and paste the code. Additionally, by returning a function, we can create reusable, composable building blocks that can be used to create complex behaviors.
Another benefit of high-order functions is that they can help to improve the readability of code. By breaking down complex behaviors into small, simple functions, it becomes much easier to understand what the code is doing. Additionally, by using high-order functions, it is possible to write more declarative code, which describes what the code should do, rather than how it should do it.
JavaScript provides several built-in high-order functions, such as Array.prototype.map(), Array.prototype.filter(), and Array.prototype.reduce(). These functions are used to perform common operations on arrays, such as mapping, filtering, and reducing elements.
The Array.prototype.map() function takes a callback function as its argument, and applies it to each element in an array, returning a new array with the results. For example, the following code doubles each element in an array:
const numbers = [1, 2, 3, 4];
const double = x => x * 2;
const doubledNumbers = numbers.map(double);
console.log(doubledNumbers); // [2, 4, 6, 8]The Array.prototype.filter() function also takes a callback function as its argument, but only includes elements in the new array for which the callback function returns true. For example, the following code filters out all odd numbers from an array:
const numbers = [1, 2, 3, 4];
const even = x => x % 2 === 0;
const evenNumbers = numbers.filter(even);
console.log(evenNumbers); // [2, 4]The Array.prototype.reduce() function takes a callback function and an initial value as arguments, and applies the callback function to each element in the array in order to reduce the array to a single value. For example, the following code calculates the sum of all elements in an array:
const numbers = [1, 2, 3, 4];
const add = (a, b) => a + b;
const sum = numbers.reduce(add, 0);
console.log(sum); // 10In addition to the built-in high-order functions provided by JavaScript, it is also possible to create custom high-order functions. For example, the following code creates a custom high-order function that takes an array and a callback function as arguments, and returns
Cheers to better composition! 🙂
Awesome!!