js-reduce-vs-filter-and-map, Use reduce instead of chains map and filter, to reduce the number of repeated passes through the array

js-reduce-vs-filter-and-map.js

// https://twitter.com/forwebdev/status/782844763942817792

const users = [{
  firstName: 'John',
  lastName: 'Black',
  age: 27
}, ...];

// bad, two passes
users
  .filter(user => user.age < 40)
  .map(({firstName, lastName}) => `${firstName} ${lastName}`);
// -> ['John Black', ...]

// good, one pass
users.reduce((acc, user) => {
  if (user.age < 40) {
    return acc.concat(`${firstName} ${lastName}`);
  }
},[]);