transduction-block01.js

const data = [
  1,
  2,
  3,
  4,
  5,
];

/**
 * 
 * This utility function is often available on various 
 * functional libraries (i.e ramdajs)
 * `pipe` is the opposite of `compose`
 */
const pipe = (...fns) => initialValue => fns.reduce((result, fn) => fn(result), initialValue);

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

const getItemsBelow10 = (x) => x < 10;
const sum = (accumulator, currentValue) => accumulator += currentValue;

const res = data
  .map(
    pipe(addBy1, multiplyBy2)
  )
  .filter(getItemsBelow10)
  .reduce(sum, 0)

// 18