simple example of compose

simple-compose.js

const makeUpperCase = (word) => word.toUpperCase();
const makePlural = (word) => word + 's';

makePlural('shoe');//=> 'shoes'
makeUpperCase('shoe');//=> 'SHOE'

const compose = (x, y) => {
  return function (z) {
    return x(y(z)); 
  };
};

const upperPlural = compose(makeUpperCase, makePlural);                           

upperPlural('feet'); //=> "FEETS"