YourJS candidate function: Takes the keys to copy from the specified subject and place in the returned object. This can be called as a partial function.

only.js

console.loadYourJS({ functions: ['has'] });

//\\
var { has } = YourJS;

//\\
// requires has()
function only(opt_subject, keys, opt_initial) {
  function f(subject, opt_initial) {
    var result = {};
    return keys.reduce(function (result, key) {
      if (has(subject, key)) {
        result[key] = subject[key];
      }
      return result;
    }, opt_initial || {});
  }

  return keys ? f(opt_subject, opt_initial) : ((keys = opt_subject), f);
}

//\\
var people = [
  'Female: Celia Cruz',
  'Male: Antonio Banderas',
  'Female: Estefania Delarosa',
  'Male: Tiago Morais',
  'Male: Victor Hughes',
  'Female: Britney Stalls'
].map(x => (([g, f, l]) => ({ gender: g, firstName: f, lastName: l }))(x.split(/:? /)));

//\\
var onlyNames = only(['firstName', 'lastName']);
people.forEach(x => console.log('Names:', onlyNames(x)));

//\\
people.forEach(x => console.log('Gender:', only(x, ['gender'])));

See it in action here:
https://www.yourjs.com/console/?gist=21095b56aa3aa03300fce3aed6f77c3b&file=only.js