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Rediscovering JavaScript: ES6, ES7 & ES8

Solution Review: Functional Style Programming

Explore how to apply functional programming techniques in JavaScript using arrow functions. Understand the use of array methods filter, map, and reduce to find, transform, and aggregate data in a concise and expressive style. This lesson enables you to write cleaner and more readable code by replacing traditional loops with functional approaches.

We'll cover the following...

Solution

The solution to the previous challenge is given below. Let’s explore it.

Javascript (babel-node)
'use strict';
const numbers = [1, 5, 2, 6, 8, 3, 4, 9, 7, 6];
console.log(
  numbers.filter(e => e % 2 === 0)
  .map(e => e * 2)
  .reduce((total, e) => total + e));

Explanation

What are we doing here? We have an array of numbers, and we are trying to get the total sum of double of all the even numbers present in that array. So, functionality consists of three steps.

  • First, find the even numbers in the array.
  • Second, double the even numbers.
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