Map, Reduce, Filter, chained usage - web dev interview, discussion

array-methods-functional.js

const animals = ['cat', 'dog', 'fish'];
const lengths = animals.map(animal => animal.length);
console.log(lengths);


const reducer = (acc, word) => acc + word.length;
const letterCount = animals.reduce(reducer, 0);
console.log(letterCount);

const hasThree = word => word.length === 3;
const threeLetterAnimals = animals.filter(hasThree);
console.log(threeLetterAnimals);


// all together now
// initial implementation
// can abstract pure functions for more reuse and clarity
// e.g. like we already did with `hasThree` earlier, reuse here
const studum = (acc, item) => {
  const word = item.charAt(0).toUpperCase() + item.slice(1);
  return acc + word; 
};
const animalsStudCaps = animals.filter(hasThree)
  .reduce(studum, '');
console.log(animalsStudCaps);

// with abstrations to pure functions
const capitalize = word => word.charAt(0).toUpperCase() + word.slice(1);
const mergeWords = (words, word) => words + word;
const animalsThreeCaps = animals.filter(hasThree)
  .map(capitalize)
  .reduce(mergeWords, '');
console.log('purified', animalsThreeCaps);