ramda.js

const R = require('ramda');

const append = (text) => (value) => value + text;
const removeTheLetter = (letter) => (sentence) => 
    sentence
    .split('')
    .filter(c => c !== letter)
    .join('');

const makeLetterUpperCase = (letter) => (sentence) => 
    sentence.split('')
    .map(c => c === letter ? c.toUpperCase() : c)
    .join('');

const removeWordsWithLessThanFourLetters = (sentence) =>
    sentence
    .split(' ')
    .filter(word => word.length > 4)
    .join(' ');