[Javascript] Improve Composition with the Compose Combinator

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To make our composition more readable and easier to name we are going to ceate a compose function we can use to avoid having to manually nest our transducer calls.

We‘ll also go over semantically naming your compose functions for extra readability.

 

Nested style:

import {doubleTheNumber, evenOnly} from "../utils";const map = xf => reducer => {  return (accumulation, value) => {    return reducer(accumulation, xf(value));  };};const filter = predicate => reducer => {  return (accumulation, value) => {    if (predicate(value)) return reducer(accumulation, value);    return accumulation;  };};const isEvenFilter = filter(evenOnly);const isNot2Filter = filter(val => val !== 2);const doubleMap = map(doubleTheNumber);const pushReducer = (accumulation, value) => {  accumulation.push(value);  return accumulation;};[1,2,3,4].reduce(isNot2Filter(isEvenFilter(doubleMap(pushReducer))), []);

 

 

Compose function:

import {filter, map, evenOnly, doubleTheNumber} from "../utils";const doubleMap = map(doubleTheNumber);const isEvenFilter = filter(evenOnly);const isNot2Filter = filter(val => val !== 2);const pushReducer = (accumulation, value) => {  accumulation.push(value);  return accumulation;};[1, 2, 3, 4].reduce(isNot2Filter(isEvenFilter(doubleMap(pushReducer))), []);// compose(f,g)(x) === f(g(x));//// compose(isNot2Filter, isEvenFilter, doubleMap)(pushReducer) ===// isNot2Filter(isEvenFilter(doubleMap(pushReducer)));const compose = (...functions) =>  functions.reduce((accumulation, fn) =>    (...args) => accumulation(fn(...args)), x => x);[1, 2, 3, 4].reduce(  compose(isNot2Filter, isEvenFilter, doubleMap)(pushReducer),  [],); /*?*/

 

[Javascript] Improve Composition with the Compose Combinator