Functional programming in Js - Map

map.js

Array.prototype.map = function(projectionFunction) {
	var results = [];
	this.forEach(function(itemInArray) {
    /*
      projectionFunction is applied to each element of the array, which returns the modified value of that element
    */
		results.push(projectionFunction(itemInArray));

	});

	return results;
};

// Example
function() {
	var popularMovies = [
			{
				"id": 1,
				"title": "Inception",
				"actors": ["Leo","Tom","Joseph"]
			},
			{
				"id": 2,
				"title": "Jason Bourne",
				"actors": ["Matt","Alicia"]
			},
      {
				"id": 3,
				"title": "Interstellar",
				"actors": ["Matthew","Matt","Anne"]
			},
      {
				"id": 4,
				"title": "Fast & Furious",
				"actors": ["Vin","Paul","Dwayne"]
			},
		];

  return popularMovies.map(function(movie) { return { id: movie.id, title: movie.title }; });
}