Function Composition in JavaScript

Introduction

In this lab, we will explore the concept of function composition in JavaScript. We will learn how to combine multiple functions to create a new function, and how to use the compose() function to perform right-to-left function composition. Through hands-on examples and exercises, we will gain a deeper understanding of this powerful technique and its practical applications in programming.

How to Compose Functions in JavaScript

To start practicing coding using function composition in JavaScript, open the Terminal/SSH and type node.

Here's an example of how to perform right-to-left function composition in JavaScript:

1. Use Array.prototype.reduce() to perform right-to-left function composition.
2. The last (rightmost) function can accept one or more arguments; the remaining functions must be unary.
3. Define the compose function that will take any number of functions as arguments and return a new function that composes them.
4. Call the compose function with the desired functions in the desired order.
5. Call the new composed function with any necessary arguments.

const compose = (...fns) =>
  fns.reduce(
    (f, g) =>
      (...args) =>
        f(g(...args))
  );

For example, let's say we have two functions:

const add5 = (x) => x + 5;
const multiply = (x, y) => x * y;

We can compose these functions using compose:

const multiplyAndAdd5 = compose(add5, multiply);

Now we can call multiplyAndAdd5 with the desired arguments:

multiplyAndAdd5(5, 2); // 15

Summary

Congratulations! You have completed the Compose Functions lab. You can practice more labs in LabEx to improve your skills.