threading

A clojure-inspired utility for threading arbitrary data into the first or last argument of a sequence of functions

Motivation

In order to compose function operations on arbitrary data, you have to nest functions

expect(subtract(add(3, 3) 3)).toBe(3);

The legibility of the example decreases as the number of functions increase.

Example Usage

Thread-first

Apply the initial & resulting values of the function list to the first argument of the function.

Simply provide an initial value then the functions you'd like to compose on the value.

import { threadFirst } from 'threading';
 
const value = threadFirst(
    5,
    timesThree,
    plusOne
);
 
expect(value).toBe(16);

To use with a function that should already have a value you can pass an array containing the function and the other arguments.

import { threadFirst } from 'threading';
 
const value = threadFirst(
  5,
  [times 3],
  [divideby 5]
);
 
expect(value).toBe(3);

Thread-last

Apply the initial & resulting values of the function list to the last argument of the function.

Simply provide an initial value then the functions you'd like to compose on the value.

import { threadLast } from 'threading';
 
const value = threadLast(
    5,
    timesThree,
    plusOne
);
 
expect(value).toBe(16);

To use with a function that should already have a value you can pass an array containing the function and the other arguments.

import { threadLast } from 'threading';
 
const value = threadFirst(
  5,
  [times 2],
  [divideby 5]
);
 
expect(value).toBe(0.5);