nth-arg

nth-arg is a utility function that returns a higher-order function to apply a given function to the nth argument of a function's argument list. It allows you to easily work with specific arguments in a function by targeting their index, including support for negative indices, similar to Array.prototype.at.

Table of Contents

- Installation
- Usage
- Basic Usage
- Currying
- Negative Indices
- API
- License

Installation

You can install nth-arg using npm or yarn:

``bash
npm install nth-arg
`

or

`bash
yarn add nth-arg
`

Usage

$3

You can directly provide a function and use nth-arg to apply it to the nth argument:

`javascript
const nth = require('nth-arg');

const getSecondArg = nth(1, x => x * 2);
console.log(getSecondArg(5, 10, 15)); // Output: 20
`

$3

If you don't provide a function, nth-arg will return a curried function that allows you to specify the function later:

`javascript
const applyToThird = nth(2);
const getThirdArgLength = applyToThird(arg => arg.length);
console.log(getThirdArgLength('a', 'bb', 'ccc')); // Output: 3
`

$3

nth-arg supports negative indices, which work similarly to Array.prototype.at, letting you access arguments from the end:

`javascript
const getLastArg = nth(-1, x => x.toUpperCase());
console.log(getLastArg('hello', 'world')); // Output: 'WORLD'
`

API

$3

Returns a function that applies fn to the nth argument of a function's argument list.

- n (number): The index of the argument in the arguments array to apply fn to. Supports negative indices.
- fn (function | undefined): The function to be applied to the nth argument. If not provided, a curried version of the function is returned.

#### Returns:
- If fn is provided, returns a function that applies fn to the nth argument.
- If fn is not provided, returns a curried function that takes a function and applies it to the nth argument.

$3

`javascript
// Basic usage with provided function
const getSecondArg = nth(1, x => x * 2);
console.log(getSecondArg(5, 10, 15)); // Output: 20

// Currying usage
const applyToThird = nth(2);
const getThirdArgLength = applyToThird(arg => arg.length);
console.log(getThirdArgLength('a', 'bb', 'ccc')); // Output: 3

// Using negative indices
const getLastArg = nth(-1, x => x.toUpperCase());
console.log(getLastArg('hello', 'world')); // Output: 'WORLD'
``

License

This project is licensed under the MIT License - see the LICENSE file for details.