var IMDBShows = [

  { name: "House of cards", rating: 9.1, users: 204420 },

  { name: "Once upon a time", rating: 8.1, users: 139421 },

  { name: "Breaking Bad", rating: 9.5, users: 664927 }

];

​

Array.prototype.map = function(projectionFunction) {

    var results = [];

    this.forEach(function(itemInArray) {

        results.push(projectionFunction(itemInArray));

​

    });

    return results;

};

​

​

function getShowNames(shows) {

  return shows.map(function(show) {

    return show.name;

  });

}

​

var shows = getShowNames(IMDBShows);

​

console.log(JSON.stringify(shows));