Flip Function Arguments

Introduction

In this lab, we will explore the concept of flipping function arguments in JavaScript. We will learn how to take a function as an argument and rearrange the arguments so that the first argument becomes the last. Through this exercise, we will gain a better understanding of argument destructuring, closures, and variadic arguments in JavaScript.

Skills Graph

Reorder Function Arguments with Flip

To swap the order of function arguments, use the flip function. This function takes a function as an argument and returns a new function that swaps the first and last arguments.

To implement flip:

• Use argument destructuring and a closure with variadic arguments.
• Splice the first argument using the spread operator (...) to make it the last argument before applying the rest.

const flip =
  (fn) =>
  (first, ...rest) =>
    fn(...rest, first);

Here's an example of how to use flip to reorder the arguments of Object.assign:

let a = { name: "John Smith" };
let b = {};

// Create a new function that swaps the arguments of Object.assign
const mergeFrom = flip(Object.assign);

// Create a new function that binds the first argument to a
let mergePerson = mergeFrom.bind(null, a);

// Call the new function with b as the second argument
mergePerson(b); // b is now equal to a

// Alternatively, merge a and b without using the new function
b = {};
Object.assign(b, a); // b is now equal to a

Summary

Congratulations! You have completed the Flip Function Arguments lab. You can practice more labs in LabEx to improve your skills.