blakek / curry

🍛 Simple curry functions

curry

🍛 Simple curry functions

A simple helper to wrap a function and gradually accept (i.e. partially apply) arguments.

This package is technically a helper partial application, but curry is much easier to remember and a nicer package function name than partiallyApply.

Install

Using Yarn:

$ yarn add @blakek/curry

…or using npm:

$ npm i --save @blakek/curry

Usage

import { curry, curryRight } from '@blakek/curry';

// Simple curry usage
const multiply = (a, b) => a * b;
const timesTwo = curry(multiply)(2);
timesTwo(5); //» 10

// Specify number of arguments
const sum = (...args) => args.reduce((a, b) => a + b, 0);
const topFiveTotal = curry(sum, 5);
topFiveTotal(1, 5, 6)(6)(7); //» 25

// Reverse arguments
const prop = (object, key) => object[key];
const getName = curryRight(prop)('name');
getName({ name: 'John Smith', age: 42 }); //» 'John Smith'

TypeScript

The types of many functions are inferred. However, some functions, such as variadic functions, need an explicit type:

const add = (...args: number[]) => args.reduce((a, b) => a + b, 0);

const addFourItems = curry(add, 4) as VariadicCurry<
  // argument types
  [number, number, number, number],
  // return type
  number
>;

// Includes helpers for functions accepting <=5 args
const addTwo = curry(add, 2) as Curry2<number, number, number>;

API

curry

curry(fn: Function, arity?: number): any;

Returns functions that take in the arguments of a function until all have been provided.

curryRight

curryRight(fn: Function, arity?: number): any;

Same as curry, but reverses all arguments once the limit has been provided. Provided for the common use-case of needing to supply context-specific arguments before providing the first arguments.

For example:

import { curryRight } from '@blakek/curry';

const users = [
  { username: 'blakek' },
  { username: 'gsandf' },
  { username: 'google' }
];

const prop = (object, key) => object[key];
const getUsername = curryRight(prop)('username');
users.map(getUsername); //» [ 'blakek', 'gsandf', 'google' ]

Contributing

Node.js and Yarn are required to work with this project.

To install all dependencies, run:

yarn

Useful Commands

yarn build	Builds the project to ./dist
yarn format	Format the source following the Prettier styles
yarn test	Run project tests
yarn test --watch	Run project tests, watching for file changes

License

MIT