transduction-block07.js

/**
 * 
 * These utility functions are often available on various 
 * functional libraries (i.e ramdajs)
 * `compose` runs from right-to-left
 * `pipe` runs from left-to-right
 */
const compose = (...fns) => (initialValue) => fns.reduceRight((d, f) => f(d), initialValue);
const pipe = (...fns) => (initialValue) => fns.reduce((d, f) => f(d), initialValue);

const data = 5;

const addBy1 = (x) => x + 1;
const multiplyBy2 = (x) => x * 2;

const composeResult = compose(multiplyBy2, addBy1)(data);

// 12

const pipeResult = pipe(addBy1, multiplyBy2)(data);

// 12