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.

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.