http://reactivex.io/learnrx/ solutions

exercise01.js

// Exercise 1: Print all the names in an array
function(console) {
	var names = ["Ben", "Jafar", "Matt", "Priya", "Brian"];

  names.map(function(name) { console.log(name); });
}
		

exercise02.js

// Exercise 2: Use forEach to print all the names in an array
function(console) {
	var names = ["Ben", "Jafar", "Matt", "Priya", "Brian"];

	names.forEach(function(name) {
		console.log(name);
	});
}

exercise03.js

// Exercise 3: Project an array of videos into an array of {id,title} pairs using forEach()
function() {
	var newReleases = [
		{
			"id": 70111470,
			"title": "Die Hard",
			"boxart": "http://cdn-0.nflximg.com/images/2891/DieHard.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": [4.0],
			"bookmark": []
		},
		{
			"id": 654356453,
			"title": "Bad Boys",
			"boxart": "http://cdn-0.nflximg.com/images/2891/BadBoys.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": [5.0],
			"bookmark": [{ id: 432534, time: 65876586 }]
		},
		{
			"id": 65432445,
			"title": "The Chamber",
			"boxart": "http://cdn-0.nflximg.com/images/2891/TheChamber.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": [4.0],
			"bookmark": []
		},
		{
			"id": 675465,
			"title": "Fracture",
			"boxart": "http://cdn-0.nflximg.com/images/2891/Fracture.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": [5.0],
			"bookmark": [{ id: 432534, time: 65876586 }]
		}
	],
	videoAndTitlePairs = [];

	// ------------ INSERT CODE HERE! -----------------------------------
	// Use forEach function to accumulate {id, title} pairs from each video.
	// Put the results into the videoAndTitlePairs array using the Array's
	// push() method. Example: videoAndTitlePairs.push(newItem);
	// ------------ INSERT CODE HERE! -----------------------------------

  videoAndTitlePairs = newReleases.map((r) => { return { id: r.id, title: r.title }; });
	return videoAndTitlePairs;
}

exercise04.js

// Exercise 4: Implement map()
Array.prototype.map = function(projectionFunction) {
	var results = [];
	this.forEach(function(itemInArray) {

		// ------------ INSERT CODE HERE! ----------------------------
		// Apply the projectionFunction to each item in the array and add
		// each result to the results array.
		// Note: you can add items to an array with the push() method.
		// ------------ INSERT CODE HERE! ----------------------------
		results.push(projectionFunction(itemInArray));
	});

	return results;
};

// JSON.stringify([1,2,3].map(function(x) { return x + 1; })) === '[2,3,4]'

exercise05.js

// Exercise 5: Use map() to project an array of videos into an array of {id,title} pairs
function() {
	var newReleases = [
		{
			"id": 70111470,
			"title": "Die Hard",
			"boxart": "http://cdn-0.nflximg.com/images/2891/DieHard.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": [4.0],
			"bookmark": []
		},
		{
			"id": 654356453,
			"title": "Bad Boys",
			"boxart": "http://cdn-0.nflximg.com/images/2891/BadBoys.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": [5.0],
			"bookmark": [{ id: 432534, time: 65876586 }]
		},
		{
			"id": 65432445,
			"title": "The Chamber",
			"boxart": "http://cdn-0.nflximg.com/images/2891/TheChamber.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": [4.0],
			"bookmark": []
		},
		{
			"id": 675465,
			"title": "Fracture",
			"boxart": "http://cdn-0.nflximg.com/images/2891/Fracture.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": [5.0],
			"bookmark": [{ id: 432534, time: 65876586 }]
		}
	];

	// ------------ INSERT CODE HERE! -----------------------------------
	// Use map function to accumulate {id, title} pairs from each video.
  return newReleases.map(function (r) { return { id, title } = r; } ); // finish this expression!
	// ------------ INSERT CODE HERE! -----------------------------------

}

exercise06.js

// Exercise 6: Use forEach() to collect only those videos with a rating of 5.0
function() {
	var newReleases = [
		{
			"id": 70111470,
			"title": "Die Hard",
			"boxart": "http://cdn-0.nflximg.com/images/2891/DieHard.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": 4.0,
			"bookmark": []
		},
		{
			"id": 654356453,
			"title": "Bad Boys",
			"boxart": "http://cdn-0.nflximg.com/images/2891/BadBoys.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": 5.0,
			"bookmark": [{ id: 432534, time: 65876586 }]
		},
		{
			"id": 65432445,
			"title": "The Chamber",
			"boxart": "http://cdn-0.nflximg.com/images/2891/TheChamber.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": 4.0,
			"bookmark": []
		},
		{
			"id": 675465,
			"title": "Fracture",
			"boxart": "http://cdn-0.nflximg.com/images/2891/Fracture.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": 5.0,
			"bookmark": [{ id: 432534, time: 65876586 }]
		}
	],
	videos = [];

	// ------------ INSERT CODE HERE! -----------------------------------
	// Use forEach function to accumulate every video with a rating of 5.0
	// ------------ INSERT CODE HERE! -----------------------------------

  return newReleases.filter((r) => {return r.rating === 5.0});
}

exercise07.js

// Exercise 7: Implement filter()
Array.prototype.filter = function(predicateFunction) {
	var results = [];
	this.forEach(function(itemInArray) {
		// ------------ INSERT CODE HERE! ----------------------------
		// Apply the predicateFunction to each item in the array.
		// If the result is truthy, add the item to the results array.
		// Note: remember you can add items to the array using the array's
		// push() method.
		// ------------ INSERT CODE HERE! ----------------------------
    if (predicateFunction(itemInArray)) results.push(itemInArray);
	});

	return results;
};

// JSON.stringify([1,2,3].filter(function(x) { return x > 2})) === "[3]"

exercise08.js

// Exercise 8: Chain filter and map to collect the ids of videos that have a rating of 5.0
function() {
	var newReleases = [
		{
			"id": 70111470,
			"title": "Die Hard",
			"boxart": "http://cdn-0.nflximg.com/images/2891/DieHard.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": 4.0,
			"bookmark": []
		},
		{
			"id": 654356453,
			"title": "Bad Boys",
			"boxart": "http://cdn-0.nflximg.com/images/2891/BadBoys.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": 5.0,
			"bookmark": [{ id: 432534, time: 65876586 }]
		},
		{
			"id": 65432445,
			"title": "The Chamber",
			"boxart": "http://cdn-0.nflximg.com/images/2891/TheChamber.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": 4.0,
			"bookmark": []
		},
		{
			"id": 675465,
			"title": "Fracture",
			"boxart": "http://cdn-0.nflximg.com/images/2891/Fracture.jpg",
			"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
			"rating": 5.0,
			"bookmark": [{ id: 432534, time: 65876586 }]
		}
	];

	// ------------ INSERT CODE HERE! -----------------------------------
	// Chain the filter and map functions to select the id of all videos
	// with a rating of 5.0.

  return newReleases.filter((r) => r.rating === 5.0).map((r) => r.id) // Complete this expression
	// ------------ INSERT CODE HERE! -----------------------------------
}

exercise09.js

// Exercise 9: Flatten the movieLists array into an array of video ids
function() {
	var movieLists = [
		{
			name: "New Releases",
			videos: [
				{
					"id": 70111470,
					"title": "Die Hard",
					"boxart": "http://cdn-0.nflximg.com/images/2891/DieHard.jpg",
					"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
					"rating": 4.0,
					"bookmark": []
				},
				{
					"id": 654356453,
					"title": "Bad Boys",
					"boxart": "http://cdn-0.nflximg.com/images/2891/BadBoys.jpg",
					"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
					"rating": 5.0,
					"bookmark": [{ id: 432534, time: 65876586 }]
				}
			]
		},
		{
			name: "Dramas",
			videos: [
				{
					"id": 65432445,
					"title": "The Chamber",
					"boxart": "http://cdn-0.nflximg.com/images/2891/TheChamber.jpg",
					"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
					"rating": 4.0,
					"bookmark": []
				},
				{
					"id": 675465,
					"title": "Fracture",
					"boxart": "http://cdn-0.nflximg.com/images/2891/Fracture.jpg",
					"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
					"rating": 5.0,
					"bookmark": [{ id: 432534, time: 65876586 }]
				}
			]
		}
	],
	allVideoIdsInMovieLists = [];

	// ------------   INSERT CODE HERE!  -----------------------------------
	// Use two nested forEach loops to flatten the movieLists into a list of
	// video ids.
	// ------------   INSERT CODE HERE!  -----------------------------------
  movieLists.forEach((list) => { list.videos.forEach((movie) => { 
    allVideoIdsInMovieLists.push(movie.id); }); });
	return allVideoIdsInMovieLists;

}
		

exercise10.js

// Exercise 10: Implement concatAll()
Array.prototype.concatAll = function() {
	var results = [];
	this.forEach(function(subArray) {
		// ------------ INSERT CODE HERE! ----------------------------
		// Add all the items in each subArray to the results array.
		// ------------ INSERT CODE HERE! ----------------------------
    subArray.forEach((item) => { results.push(item); });
	});

	return results;
};

// JSON.stringify([ [1,2,3], [4,5,6], [7,8,9] ].concatAll()) === "[1,2,3,4,5,6,7,8,9]"
// [1,2,3].concatAll(); // throws an error because this is a one-dimensional array

exercise11.js

// Exercise 11: Use map() and concatAll() to project and flatten the movieLists into an array of video ids
function() {
	var movieLists = [
			{
				name: "New Releases",
				videos: [
					{
						"id": 70111470,
						"title": "Die Hard",
						"boxart": "http://cdn-0.nflximg.com/images/2891/DieHard.jpg",
						"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 4.0,
						"bookmark": []
					},
					{
						"id": 654356453,
						"title": "Bad Boys",
						"boxart": "http://cdn-0.nflximg.com/images/2891/BadBoys.jpg",
						"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 5.0,
						"bookmark": [{ id: 432534, time: 65876586 }]
					}
				]
			},
			{
				name: "Dramas",
				videos: [
					{
						"id": 65432445,
						"title": "The Chamber",
						"boxart": "http://cdn-0.nflximg.com/images/2891/TheChamber.jpg",
						"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 4.0,
						"bookmark": []
					},
					{
						"id": 675465,
						"title": "Fracture",
						"boxart": "http://cdn-0.nflximg.com/images/2891/Fracture.jpg",
						"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 5.0,
						"bookmark": [{ id: 432534, time: 65876586 }]
					}
				]
			}
		];

	return movieLists.
	  map(function(movieList) {
		return movieList.videos.map(function(video) {
			return video.id;
		  });
	  }).
	  concatAll();

}

exercise12.js

// Exercise 12: Retrieve id, title, and a 150x200 box art url for every video
function() {
	var movieLists = [
			{
				name: "Instant Queue",
				videos : [
					{
						"id": 70111470,
						"title": "Die Hard",
						"boxarts": [
							{ width: 150, height: 200, url: "http://cdn-0.nflximg.com/images/2891/DieHard150.jpg" },
							{ width: 200, height: 200, url: "http://cdn-0.nflximg.com/images/2891/DieHard200.jpg" }
						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 4.0,
						"bookmark": []
					},
					{
						"id": 654356453,
						"title": "Bad Boys",
						"boxarts": [
							{ width: 200, height: 200, url: "http://cdn-0.nflximg.com/images/2891/BadBoys200.jpg" },
							{ width: 150, height: 200, url: "http://cdn-0.nflximg.com/images/2891/BadBoys150.jpg" }

						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 5.0,
						"bookmark": [{ id: 432534, time: 65876586 }]
					}
				]
			},
			{
				name: "New Releases",
				videos: [
					{
						"id": 65432445,
						"title": "The Chamber",
						"boxarts": [
							{ width: 150, height: 200, url: "http://cdn-0.nflximg.com/images/2891/TheChamber150.jpg" },
							{ width: 200, height: 200, url: "http://cdn-0.nflximg.com/images/2891/TheChamber200.jpg" }
						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 4.0,
						"bookmark": []
					},
					{
						"id": 675465,
						"title": "Fracture",
						"boxarts": [
							{ width: 200, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture200.jpg" },
							{ width: 150, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture150.jpg" },
							{ width: 300, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture300.jpg" }
						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 5.0,
						"bookmark": [{ id: 432534, time: 65876586 }]
					}
				]
			}
		];

	return movieLists.
    map(l => l.videos)
    .concatAll()
    .map(v => v.boxarts.map(b => {
         return { id: v.id, title: v.title, boxart: b };
         })
    .filter(v => v.boxart.width === 150)
      .map( v => { return { id: v.id, title: v.title, boxart: v.boxart.url }; }))
        .concatAll();

}
		

exercise13.js

// Exercise 13: Implement concatMap()
Array.prototype.concatMap = function(projectionFunctionThatReturnsArray) {
	return this.
		map(function(item) {
			// ------------   INSERT CODE HERE!  ----------------------------
			// Apply the projection function to each item. The projection
			// function will return a new child array. This will create a
			// two-dimensional array.
			// ------------   INSERT CODE HERE!  ----------------------------
      return projectionFunctionThatReturnsArray(item);
		}).
		// apply the concatAll function to flatten the two-dimensional array
		concatAll();
};

/*
	var spanishFrenchEnglishWords = [ ["cero","rien","zero"], ["uno","un","one"], ["dos","deux","two"] ];
	// collect all the words for each number, in every language, in a single, flat list
	var allWords = [0,1,2].
		concatMap(function(index) {
			return spanishFrenchEnglishWords[index];
		});

	return JSON.stringify(allWords) === '["cero","rien","zero","uno","un","one","dos","deux","two"]';
*/
		

exercise14.js

// Exercise 14: Use concatMap() to retrieve id, title, and 150x200 box art url for every video
function() {
	var movieLists = [
			{
				name: "Instant Queue",
				videos : [
					{
						"id": 70111470,
						"title": "Die Hard",
						"boxarts": [
							{ width: 150, height: 200, url: "http://cdn-0.nflximg.com/images/2891/DieHard150.jpg" },
							{ width: 200, height: 200, url: "http://cdn-0.nflximg.com/images/2891/DieHard200.jpg" }
						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 4.0,
						"bookmark": []
					},
					{
						"id": 654356453,
						"title": "Bad Boys",
						"boxarts": [
							{ width: 200, height: 200, url: "http://cdn-0.nflximg.com/images/2891/BadBoys200.jpg" },
							{ width: 150, height: 200, url: "http://cdn-0.nflximg.com/images/2891/BadBoys150.jpg" }

						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 5.0,
						"bookmark": [{ id: 432534, time: 65876586 }]
					}
				]
			},
			{
				name: "New Releases",
				videos: [
					{
						"id": 65432445,
						"title": "The Chamber",
						"boxarts": [
							{ width: 150, height: 200, url: "http://cdn-0.nflximg.com/images/2891/TheChamber150.jpg" },
							{ width: 200, height: 200, url: "http://cdn-0.nflximg.com/images/2891/TheChamber200.jpg" }
						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 4.0,
						"bookmark": []
					},
					{
						"id": 675465,
						"title": "Fracture",
						"boxarts": [
							{ width: 200, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture200.jpg" },
							{ width: 150, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture150.jpg" },
							{ width: 300, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture300.jpg" }
						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 5.0,
						"bookmark": [{ id: 432534, time: 65876586 }]
					}
				]
			}
		];


	// Use one or more concatMap, map, and filter calls to create an array with the following items
	// [
	//	 {"id": 675465, "title": "Fracture", "boxart": "http://cdn-0.nflximg.com/images/2891/Fracture150.jpg" },
	//	 {"id": 65432445, "title": "The Chamber", "boxart": "http://cdn-0.nflximg.com/images/2891/TheChamber150.jpg" },
	//	 {"id": 654356453, "title": "Bad Boys", "boxart": "http://cdn-0.nflximg.com/images/2891/BadBoys150.jpg" },
	//	 {"id": 70111470, "title": "Die Hard", "boxart": "http://cdn-0.nflximg.com/images/2891/DieHard150.jpg" }
	// ];

	return movieLists.concatMap(l => l.videos)
    .concatMap(v => v.boxarts.filter(b => b.width === 150)
    .map(a => { return { id: v.id, title: v.title, boxart: a.url } }))
    // Complete this expression!

}
		

exercise15.js

// Exercise 15: Use forEach to find the largest box art
function() {
	var boxarts = [
			{ width: 200, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture200.jpg" },
			{ width: 150, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture150.jpg" },
			{ width: 300, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture300.jpg" },
			{ width: 425, height: 150, url: "http://cdn-0.nflximg.com/images/2891/Fracture425.jpg" }
		],
		currentSize,
		maxSize = -1,
		largestBoxart;

	boxarts.forEach(function(boxart) {
		currentSize = boxart.width * boxart.height;
		if (currentSize > maxSize) {
			largestBoxart = boxart;
			maxSize = currentSize;
		}
	});

	return largestBoxart;
}
		

exercise16.js

// Exercise 16: Implement reduce()
// [1,2,3].reduce(function(accumulatedValue, currentValue) { return accumulatedValue + currentValue; }); === [6];
// [1,2,3].reduce(function(accumulatedValue, currentValue) { return accumulatedValue + currentValue; }, 10); === [16];

Array.prototype.reduce = function(combiner, initialValue) {
	var counter,
		accumulatedValue;

	// If the array is empty, do nothing
	if (this.length === 0) {
		return this;
	}
	else {
		// If the user didn't pass an initial value, use the first item.
		if (arguments.length === 1) {
			counter = 1;
			accumulatedValue = this[0];
		}
		else if (arguments.length >= 2) {
			counter = 0;
			accumulatedValue = initialValue;
		}
		else {
			throw "Invalid arguments.";
		}

		// Loop through the array, feeding the current value and the result of
		// the previous computation back into the combiner function until
		// we've exhausted the entire array and are left with only one value.
		while(counter < this.length) {
			accumulatedValue = combiner(accumulatedValue, this[counter])
			counter++;
		}

		return [accumulatedValue];
	}
};
		

exercise17.js

// Exercise 17: Retrieve the largest rating.
function() {
	var ratings = [2,3,1,4,5];

	// You should return an array containing only the largest rating. Remember that reduce always
	// returns an array with one item.
	return ratings.
    reduce((a,b) => (b > a) ? b : a)   // Complete this expression
}
		

exercise18.js

// Exercise 18: Retrieve url of the largest boxart
function() {
	var boxarts = [
			{ width: 200, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture200.jpg" },
			{ width: 150, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture150.jpg" },
			{ width: 300, height: 200, url: "http://cdn-0.nflximg.com/images/2891/Fracture300.jpg" },
			{ width: 425, height: 150, url: "http://cdn-0.nflximg.com/images/2891/Fracture425.jpg" }
		];

	// You should return an array containing only the URL of the largest box art. Remember that reduce always
	// returns an array with one item.
	return boxarts.
    reduce((a, b) => (b.width > a.width) ? b : a)
    .map(b => b.url)// Complete this expression
}
		

exercise19.js

// Exercise 19: Reducing with an initial value
function() {
	var videos = [
		{
			"id": 65432445,
			"title": "The Chamber"
		},
		{
			"id": 675465,
			"title": "Fracture"
		},
		{
			"id": 70111470,
			"title": "Die Hard"
		},
		{
			"id": 654356453,
			"title": "Bad Boys"
		}
	];

	// Expecting this output...
	// [
	//	 {
	//		 "65432445": "The Chamber",
	//		 "675465": "Fracture",
	//		 "70111470": "Die Hard",
	//		 "654356453": "Bad Boys"
	//	 }
	// ]
	return videos.
		reduce(function(accumulatedMap, video) {
		var obj = {};

		// ----- INSERT CODE TO ADD THE VIDEO TITLE TO THE ----
		// ----- NEW MAP USING THE VIDEO ID AS THE KEY	 ----
    obj[video.id] = video.title;

		// Object.assign() takes all of the enumerable properties from
		// the object listed in its second argument (obj) and assigns them
		// to the object listed in its first argument (accumulatedMap).
		return Object.assign(accumulatedMap, obj);
		},
		// Use an empty map as the initial value instead of the first item in
		// the list.
		{});
}
		

exercise20.js

// Exercise 20: Retrieve the id, title, and smallest box art url for every video.
function() {
	var movieLists = [
		{
			name: "New Releases",
			videos: [
				{
					"id": 70111470,
					"title": "Die Hard",
					"boxarts": [
						{ width: 150, height:200, url:"http://cdn-0.nflximg.com/images/2891/DieHard150.jpg" },
						{ width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/DieHard200.jpg" }
					],
					"url": "http://api.netflix.com/catalog/titles/movies/70111470",
					"rating": 4.0,
					"bookmark": []
				},
				{
					"id": 654356453,
					"title": "Bad Boys",
					"boxarts": [
						{ width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/BadBoys200.jpg" },
						{ width: 140, height:200, url:"http://cdn-0.nflximg.com/images/2891/BadBoys140.jpg" }

					],
					"url": "http://api.netflix.com/catalog/titles/movies/70111470",
					"rating": 5.0,
					"bookmark": [{ id:432534, time:65876586 }]
				}
			]
		},
		{
			name: "Thrillers",
			videos: [
				{
					"id": 65432445,
					"title": "The Chamber",
					"boxarts": [
						{ width: 130, height:200, url:"http://cdn-0.nflximg.com/images/2891/TheChamber130.jpg" },
						{ width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/TheChamber200.jpg" }
					],
					"url": "http://api.netflix.com/catalog/titles/movies/70111470",
					"rating": 4.0,
					"bookmark": []
				},
				{
					"id": 675465,
					"title": "Fracture",
					"boxarts": [
						{ width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/Fracture200.jpg" },
						{ width: 120, height:200, url:"http://cdn-0.nflximg.com/images/2891/Fracture120.jpg" },
						{ width: 300, height:200, url:"http://cdn-0.nflximg.com/images/2891/Fracture300.jpg" }
					],
					"url": "http://api.netflix.com/catalog/titles/movies/70111470",
					"rating": 5.0,
					"bookmark": [{ id:432534, time:65876586 }]
				}
			]
		}
	];


	// Use one or more concatMap, map, and reduce calls to create an array with the following items (order doesn't matter)
	// [
	//	 {"id": 675465,"title": "Fracture","boxart":"http://cdn-0.nflximg.com/images/2891/Fracture120.jpg" },
	//	 {"id": 65432445,"title": "The Chamber","boxart":"http://cdn-0.nflximg.com/images/2891/TheChamber130.jpg" },
	//	 {"id": 654356453,"title": "Bad Boys","boxart":"http://cdn-0.nflximg.com/images/2891/BadBoys140.jpg" },
	//	 {"id": 70111470,"title": "Die Hard","boxart":"http://cdn-0.nflximg.com/images/2891/DieHard150.jpg" }
	// ];

	return movieLists.
		concatMap((movieList) => movieList.videos)
    .concatMap((v) => v.boxarts.reduce((a,b) => (b.width < a.width) ? b : a)
      .map(b => { return { id: v.id, title: v.title, boxart: b.url }; }))

}
		

exercise21.js

// Exercise 21: Combine videos and bookmarks by index
function() {
	var videos = [
			{
				"id": 70111470,
				"title": "Die Hard",
				"boxart": "http://cdn-0.nflximg.com/images/2891/DieHard.jpg",
				"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
				"rating": 4.0,
			},
			{
				"id": 654356453,
				"title": "Bad Boys",
				"boxart": "http://cdn-0.nflximg.com/images/2891/BadBoys.jpg",
				"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
				"rating": 5.0,
			},
			{
				"id": 65432445,
				"title": "The Chamber",
				"boxart": "http://cdn-0.nflximg.com/images/2891/TheChamber.jpg",
				"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
				"rating": 4.0,
			},
			{
				"id": 675465,
				"title": "Fracture",
				"boxart": "http://cdn-0.nflximg.com/images/2891/Fracture.jpg",
				"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
				"rating": 5.0,
			}
		],
		bookmarks = [
			{id: 470, time: 23432},
			{id: 453, time: 234324},
			{id: 445, time: 987834}
		],
	counter,
	videoIdAndBookmarkIdPairs = [];

	for(counter = 0; counter < Math.min(videos.length, bookmarks.length); counter++) {
		// Insert code here to create a {videoId, bookmarkId} pair and add it to the videoIdAndBookmarkIdPairs array.
    videoIdAndBookmarkIdPairs.push({ videoId: videos[counter].id, bookmarkId: bookmarks[counter].id });
  }

	return videoIdAndBookmarkIdPairs;
}
		

exercise22.js

// Exercise 22: Implement zip
// JSON.stringify(Array.zip([1,2,3],[4,5,6], function(left, right) { return left + right })) === '[5,7,9]'

Array.zip = function(left, right, combinerFunction) {
	var counter,
		results = [];

	for(counter = 0; counter < Math.min(left.length, right.length); counter++) {
		// Add code here to apply the combinerFunction to the left and right-hand items in the respective arrays
		results.push(combinerFunction(left[counter], right[counter]))
  }

	return results;
};
		

exercise23.js

// Exercise 23: Combine videos and bookmarks by index
function() {
	var videos = [
			{
				"id": 70111470,
				"title": "Die Hard",
				"boxart": "http://cdn-0.nflximg.com/images/2891/DieHard.jpg",
				"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
				"rating": 4.0,
			},
			{
				"id": 654356453,
				"title": "Bad Boys",
				"boxart": "http://cdn-0.nflximg.com/images/2891/BadBoys.jpg",
				"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
				"rating": 5.0,
			},
			{
				"id": 65432445,
				"title": "The Chamber",
				"boxart": "http://cdn-0.nflximg.com/images/2891/TheChamber.jpg",
				"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
				"rating": 4.0,
			},
			{
				"id": 675465,
				"title": "Fracture",
				"boxart": "http://cdn-0.nflximg.com/images/2891/Fracture.jpg",
				"uri": "http://api.netflix.com/catalog/titles/movies/70111470",
				"rating": 5.0,
			}
		],
		bookmarks = [
			{id: 470, time: 23432},
			{id: 453, time: 234324},
			{id: 445, time: 987834}
		];

	return Array.
    zip(videos, bookmarks, (v, b) => { return { videoId: v.id, bookmarkId: b.id }; }) //... finish this expression
}
		

exercise24.js

// Exercise 24: Retrieve each video's id, title, middle interesting moment time, and smallest box art url.
function() {
	var movieLists = [
			{
				name: "New Releases",
				videos: [
					{
						"id": 70111470,
						"title": "Die Hard",
						"boxarts": [
							{ width: 150, height:200, url:"http://cdn-0.nflximg.com/images/2891/DieHard150.jpg" },
							{ width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/DieHard200.jpg" }
						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 4.0,
						"interestingMoments": [
							{ type: "End", time:213432 },
							{ type: "Start", time: 64534 },
							{ type: "Middle", time: 323133}
						]
					},
					{
						"id": 654356453,
						"title": "Bad Boys",
						"boxarts": [
							{ width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/BadBoys200.jpg" },
							{ width: 140, height:200, url:"http://cdn-0.nflximg.com/images/2891/BadBoys140.jpg" }

						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 5.0,
						"interestingMoments": [
							{ type: "End", time:54654754 },
							{ type: "Start", time: 43524243 },
							{ type: "Middle", time: 6575665}
						]
					}
				]
			},
			{
				name: "Instant Queue",
				videos: [
					{
						"id": 65432445,
						"title": "The Chamber",
						"boxarts": [
							{ width: 130, height:200, url:"http://cdn-0.nflximg.com/images/2891/TheChamber130.jpg" },
							{ width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/TheChamber200.jpg" }
						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 4.0,
						"interestingMoments": [
							{ type: "End", time:132423 },
							{ type: "Start", time: 54637425 },
							{ type: "Middle", time: 3452343}
						]
					},
					{
						"id": 675465,
						"title": "Fracture",
						"boxarts": [
							{ width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/Fracture200.jpg" },
							{ width: 120, height:200, url:"http://cdn-0.nflximg.com/images/2891/Fracture120.jpg" },
							{ width: 300, height:200, url:"http://cdn-0.nflximg.com/images/2891/Fracture300.jpg" }
						],
						"url": "http://api.netflix.com/catalog/titles/movies/70111470",
						"rating": 5.0,
						"interestingMoments": [
							{ type: "End", time:45632456 },
							{ type: "Start", time: 234534 },
							{ type: "Middle", time: 3453434}
						]
					}
				]
			}
		];

	//------------ COMPLETE THIS EXPRESSION --------------
	return movieLists.
		concatMap((movieList) => movieList.videos)
    .concatMap((v) => Array.zip(v.interestingMoments.filter(a => a.type === 'Middle'), 
      v.boxarts.reduce((a,b) => b.width < a.width ? b : a), 
        (m, b) => { return { id: v.id, title: v.title, time: m.time, 
                          url: b.url }; } ));

}

exercise25.js

// Exercise 25: Converting from Arrays to Trees

function() {
	var lists = [
			{
				"id": 5434364,
				"name": "New Releases"
			},
			{
				"id": 65456475,
				"name": "Thrillers"
			}
		],
		videos = [
			{
				"listId": 5434364,
				"id": 65432445,
				"title": "The Chamber"
			},
			{
				"listId": 5434364,
				"id": 675465,
				"title": "Fracture"
			},
			{
				"listId": 65456475,
				"id": 70111470,
				"title": "Die Hard"
			},
			{
				"listId": 65456475,
				"id": 654356453,
				"title": "Bad Boys"
			}
		];

  return lists.map(c => { return { name: c.name, videos: videos
                   .filter(v => v.listId === c.id).map(v => { return { id: v.id, title: v.title }; })} }) // complete this expression
}
		

exercise26.js

// Exercise 26: Converting from Arrays to Deeper Trees
function() {
	var lists = [
			{
				"id": 5434364,
				"name": "New Releases"
			},
			{
				"id": 65456475,
				name: "Thrillers"
			}
		],
		videos = [
			{
				"listId": 5434364,
				"id": 65432445,
				"title": "The Chamber"
			},
			{
				"listId": 5434364,
				"id": 675465,
				"title": "Fracture"
			},
			{
				"listId": 65456475,
				"id": 70111470,
				"title": "Die Hard"
			},
			{
				"listId": 65456475,
				"id": 654356453,
				"title": "Bad Boys"
			}
		],
		boxarts = [
			{ videoId: 65432445, width: 130, height:200, url:"http://cdn-0.nflximg.com/images/2891/TheChamber130.jpg" },
			{ videoId: 65432445, width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/TheChamber200.jpg" },
			{ videoId: 675465, width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/Fracture200.jpg" },
			{ videoId: 675465, width: 120, height:200, url:"http://cdn-0.nflximg.com/images/2891/Fracture120.jpg" },
			{ videoId: 675465, width: 300, height:200, url:"http://cdn-0.nflximg.com/images/2891/Fracture300.jpg" },
			{ videoId: 70111470, width: 150, height:200, url:"http://cdn-0.nflximg.com/images/2891/DieHard150.jpg" },
			{ videoId: 70111470, width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/DieHard200.jpg" },
			{ videoId: 654356453, width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/BadBoys200.jpg" },
			{ videoId: 654356453, width: 140, height:200, url:"http://cdn-0.nflximg.com/images/2891/BadBoys140.jpg" }
		],
		bookmarks = [
			{ videoId: 65432445, time: 32432 },
			{ videoId: 675465, time: 3534543 },
			{ videoId: 70111470, time: 645243 },
			{ videoId: 654356453, time: 984934 }
		];

  return lists.map((c) => 
    { return { name: c.name, videos: 
      videos.filter(g => g.listId === c.id).concatMap(v => Array.zip(
      boxarts.filter(a => a.videoId === v.id).reduce((a, b) => b.width < a.width ? b : a),
      bookmarks.filter(a => a.videoId === v.id),
          (arts, book) => { return { id: v.id, title: v.title, 
                           time: book.time, boxart: arts.url }; } )) } })

                             // complete this expression

}
		

exercise27.js

// Exercise 27: Stock Ticker
function(pricesNASDAQ, printRecord) {
	var microsoftPrices,
		now = new Date(),
		tenDaysAgo = new Date( now.getFullYear(), now.getMonth(), now.getDate() - 10);

	// use filter() to filter the trades for MSFT prices recorded any time after 10 days ago
	microsoftPrices =
		pricesNASDAQ.
			filter(function(priceRecord) {	 // finish this expression
        return priceRecord.name === 'MSFT' })
	// Print the trades to the output console
	microsoftPrices.
		forEach(function(priceRecord) {
			printRecord(priceRecord);
		});
}

exercise28.js

// Exercise 28: Subscribing to an event
function(button) {
	// the button click handler
	var handler = function(ev) {
		// Unsubscribe from the button event.
		button.removeEventListener("click", handler);

		alert("Button was clicked. Unsubscribing from event.");
	};

	// add the button click handler
	button.addEventListener("click", handler);
}
		

exercise29.js

// Exercise 29: Traversing an Event
function(button) {
	var buttonClicks = Observable.fromEvent(button, "click");

	// In the case of an Observable, forEach returns a subscription object.
	var subscription =
		buttonClicks.
			forEach(function(clickEvent) {
				alert("Button was clicked. Stopping Traversal.");

				// Stop traversing the button clicks
				subscription.dispose();
			});
}
		

exercise30.js

// Exercise 30: Completing Sequences with take()
function(button) {
	var buttonClicks = Observable.fromEvent(button, "click");

	// Use take() to listen for only one button click
	// and unsubscribe.
	buttonClicks.
		take(1).
		forEach(function() {
			alert("Button was clicked once. Stopping Traversal.");
		});
}
		

exercise31.js

// Exercise 31: Completing sequences with takeUntil()
function(pricesNASDAQ, printRecord, stopButton) {
	var stopButtonClicks = Observable.fromEvent(stopButton, "click");// ----- To finish this expression, use Observable.fromEvent to convert the "click" event on the stop button to an Observable
		microsoftPrices =
			pricesNASDAQ.
				filter(function(priceRecord) {
					return priceRecord.name === "MSFT";
				}).takeUntil(stopButtonClicks)
				// ----- To finish this expression, use takeUntil to complete the sequence when stopButtonClicks fires.

	microsoftPrices.
		forEach(function(priceRecord) {
			printRecord(priceRecord);
		});
}

exercise32.js

// Exercise 32: Creating a mouse drag event
function(sprite, spriteContainer) {
	var spriteMouseDowns = Observable.fromEvent(sprite, "mousedown"),
		spriteContainerMouseMoves = Observable.fromEvent(spriteContainer, "mousemove"),
		spriteContainerMouseUps = Observable.fromEvent(spriteContainer, "mouseup"),
		spriteMouseDrags =
			// For every mouse down event on the sprite...
			spriteMouseDowns.
				concatMap((contactPoint) => spriteContainerMouseMoves.
						// ...until a mouse up event occurs.
						takeUntil(spriteContainerMouseUps)
				);

	// For each mouse drag event, move the sprite to the absolute page position.
	spriteMouseDrags.forEach(function(dragPoint) {
		sprite.style.left = dragPoint.pageX + "px";
		sprite.style.top = dragPoint.pageY + "px";
	});
}
        

exercise33.js

// Exercise 33: Improving our mouse drag event
function(sprite, spriteContainer) {
	// All of the mouse event sequences look like this:
	// seq([ {pageX: 22, pageY: 3423, layerX: 14, layerY: 22} ,,, ])
	var spriteMouseDowns = Observable.fromEvent(sprite, "mousedown"),
		spriteContainerMouseMoves = Observable.fromEvent(spriteContainer, "mousemove"),
		spriteContainerMouseUps = Observable.fromEvent(spriteContainer, "mouseup"),
		// Create a sequence that looks like this:
		// seq([ {pageX: 22, pageY:4080 },,,{pageX: 24, pageY: 4082},,, ])
		spriteMouseDrags =
			// For every mouse down event on the sprite...
			spriteMouseDowns.
				concatMap(function(contactPoint) {
					// ...retrieve all the mouse move events on the sprite container...
					return spriteContainerMouseMoves.
						// ...until a mouse up event occurs.
						takeUntil(spriteContainerMouseUps).
						map((c) => {
							return {
								pageX: c.pageX - contactPoint.layerX,
								pageY: c.pageY - contactPoint.layerY
							};
						});
				});

	// For each mouse drag event, move the sprite to the absolute page position.
	spriteMouseDrags.forEach(function(dragPoint) {
		sprite.style.left = dragPoint.pageX + "px";
		sprite.style.top = dragPoint.pageY + "px";
	});
}
        

exercise34.js

// Exercise 34: HTTP requests
function($) {
	$.getJSON(
		"http://api-global.netflix.com/queue",
		{
			success: function(json) {
				alert("Data has arrived.");
			},
			error: function(ex) {
				alert("There was an error.")
			}
		});
}

exercise35.js

// Exercise 35: Sequencing HTTP requests with callbacks
function(window, $, showMovieLists, showError) {
	var error,
		configDone,
		movieLists,
		queueList,
		windowLoaded,
		outputDisplayed,
		errorHandler = function() {
			// Otherwise show the error.
			error = "There was a connectivity error";

			// We may be ready to display out
			tryToDisplayOutput();
		},
		tryToDisplayOutput = function() {
			if (outputDisplayed) {
				return;
			}
			if (windowLoaded) {
				if (configDone && movieLists !== undefined) {
					if (queueList !== undefined) {
						movieLists.push(queueList);
					}
					outputDisplayed = true;
					showMovieLists(JSON.stringify(movieLists));
				}
				else if (error) {
					outputDisplayed = true;
					showError(error);
				}
			}
		},
		windowLoadHandler = function() {
			windowLoaded = true;

			// Remember to unsubscribe from events
			window.removeEventListener("load", windowLoadHandler);

			// This may be the last task we're waiting on, so try and display output.
			tryToDisplayOutput();
		};

	// Register for the load event
	window.addEventListener("load", windowLoadHandler);

	// Request the service url prefix for the users AB test
	$.getJSON(
		"http://api-global.netflix.com/abTestInformation",
		{
			success: function(abTestInformation) {
				// Request the member's config information to determine whether their instant
				// queue should be displayed.
				$.getJSON(
					"http://api-global.netflix.com/" + abTestInformation.urlPrefix + "/config",
					{
						success: function(config) {
							// Parallel retrieval of movie list could've failed,
							// in which case we don't want to issue this call.
							if (!error) {
								// If we're supposed to
								if (config.showInstantQueue) {
									$.getJSON(
										"http://api-global.netflix.com/" + abTestInformation.urlPrefix + "/queue",
										{
											success: function(queueMessage) {
												queueList = queueMessage.list;

												configDone = true;
												tryToDisplayOutput();
											},
											error: errorHandler
										});
								}
								else {
									configDone = true;
									tryToDisplayOutput();
								}
							}
						},
						error: errorHandler
					});

				// Retrieve the movie list
				$.getJSON(
					"http://api-global.netflix.com/" + abTestInformation.urlPrefix + "/movieLists",
					{
						success: function(movieListMessage) {
							movieLists = movieListMessage.list;
							tryToDisplayOutput();
						},
						error: errorHandler
					});
			},
			error: errorHandler
		});
}

exercise36.js

// Exercise 36: Traversing callback-based Asynchronous APIs
function(window, $) {
	var getJSON = function(url) {
		return Observable.create(function(observer) {
			var subscribed = true;

			$.getJSON(url,
				{
					success:
						function(data) {
							// If client is still interested in the results, send them.
							if (subscribed) {
								// Send data to the client
								observer.next(data);
								// Immediately complete the sequence
								observer.complete();
							}
						},
					error: function(ex) {
						// If client is still interested in the results, send them.
						if (subscribed) {
							// Inform the client that an error occurred.
							observer.error(ex);
						}
					}
				});

			// Definition of the Subscription objects unsubscribe (dispose in RxJS 4) method.
			return function() {
				subscribed = false;
			}
		});
	};

	var observer = {
		// onNext in RxJS 4
		next: function (data) {
			alert(JSON.stringify(data));
		},
		// onError in RxJS 4
		error: function (err) {
			alert(err);
		},
		// onComplete in RxJS 4
		complete: function () {
			alert("The asynchronous operation has completed.");
		}
	};

	var subscription =
		getJSON("http://api-global.netflix.com/abTestInformation").subscribe(observer);

	// setTimeout(function () {
	// 	alert("Changed my mind, I do not want notifications any more!")
	// 	subscription.unsubscribe();
	// }, 10);
}
		

exercise37.js

// Exercise 37: Sequencing HTTP requests with Observable
function(window, getJSON, showMovieLists, showError) {
	var movieListsSequence =
		Observable.zip(
			getJSON("http://api-global.netflix.com/abTestInformation").
				concatMap(function(abTestInformation) {
					return Observable.zip(
						getJSON("http://api-global.netflix.com/" + abTestInformation.urlPrefix + "/config").
							concatMap(function(config) {
								if (config.showInstantQueue) {
									return getJSON("http://api-global.netflix.com/" + abTestInformation.urlPrefix + "/queue").
										map(function(queueMessage) {
											return queueMessage.list;
										});
								}
								else {
									return Observable.returnValue(undefined);
								}
							}),
						getJSON("http://api-global.netflix.com/" + abTestInformation.urlPrefix + "/movieLists"),
						function(queue, movieListsMessage) {
							var copyOfMovieLists = Object.create(movieListsMessage.list);
							if (queue !== undefined) {
								copyOfMovieLists.push(queue);
							}

							return copyOfMovieLists;
						});
				}),
			Observable.fromEvent(window, "load"),
			function(movieLists, loadEvent) {
				return movieLists;
			});

	movieListsSequence.
		forEach(
			function(movieLists) {
				showMovieLists(movieLists);
			},
			function(err) {
				showError(err);
			});
}
		

exercise38.js

// Exercise 38: Throttle Input
function (clicks, saveData, name) {
	return clicks.
		throttleTime(1000).
		concatMap(function () {
			return saveData(name);
		})
}
        

exercise39.js

// Exercise 39: Autocomplete Box
function (getSearchResultSet, keyPresses, textBox) {

	var getSearchResultSets =
		keyPresses.
		map(function () {
			return textBox.value;
		}).
      throttleTime(1000).
		// TODO: Ensure that we only trigger a maximum of one search request per second
		concatMap(function (text) {

		// TODO: Ensure this sequence ends as soon as another key press arrives
		return getSearchResultSet(text).takeUntil(keyPresses);
	});

	return getSearchResultSets;
}
		

exercise40.js

// Exercise 40: Distinct Until Changed Input
function (keyPresses, isAlpha) {

	return keyPresses.
		map(function (e) { return String.fromCharCode(e.keyCode); }).

		// Ensure we only have alphabetic characters
		filter(function (character) { return isAlpha(character); }).

		// TODO: Filter out successive repetitive keys
		distinctUntilChanged().
		// Building up a string of all the characters typed.
		scan(function (stringSoFar, character) {
			return stringSoFar + character;
		}, '');
}
		

exercise41.js

// Exercise 41: Autocomplete Box Part 2: Electric Boogaloo
function (getSearchResultSet, keyPresses, textBox) {

	var getSearchResultSets =
		keyPresses.
			map(function () {
				return textBox.value;
			}).
			throttleTime(1000).

			// TODO: Make sure we only get distinct values
			distinctUntilChanged().

			// TODO: Make sure the text is not empty
			filter((v) => v.length > 0).
			concatMap(function (text) {
				return getSearchResultSet(text).takeUntil(keyPresses);
			});

	return getSearchResultSets;
}