Functional Programming in Javascript

chain-1.js

'use strict';

function chain() {
  var newReleases = [{
    "id": 70111470,
    "title": "Die Hard",
    "rating": 4.0
  }, {
    "id": 654356453,
    "title": "Bad Boys",
    "rating": 5.0
  }, {
    "id": 65432445,
    "title": "The Chamber",
    "rating": 4.0
  }, {
    "id": 675465,
    "title": "Fracture",
    "rating": 5.0
  }];

  var result = [];

  return newReleases.
    filter(video => video.rating === 5.0).
    map(video => video.id);
}

console.log(chain());
/*
[654356453, 675465]
*/

declarative.js

'use strict';

function declarativeSquare(arr) {
	/* You have to specify the followings :
    	1. Logic
  	*/
	return arr.map(function(val) {
  		return val*val; 
  });
}

var a = [1, 2, 3, 4, 5];
console.log(declarativeSquare(a)); // [1, 4, 9, 16, 25]

flattenThreeLevelNestedTree.js

'use strict';

function flattenThreeLevelNestedTree() {
  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"
      }]
    }, {
      "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"
      }]
    }]
  }, {
    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"
      }]
    }, {
      "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"
      }]
    }]
  }];


  // Use one or more map, concatAll, 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.map((movie) => {
    return movie.videos.map((video) => {
      return video.boxarts.filter((boxart) => {
        return boxart.width === 150;
      }).map((item) => {
        return {
          "id": video.id,
          "title": video.title,
          "boxart": item.url
        };
      })
    }).concatAll();
  }).concatAll();
}

console.log(flattenThreeLevelNestedTree());

imperative.js

'use strict';

function imperativeSquare(arr) {
  /* You have to specify the followings :
      1. How to loop throgh the array
      2. The order of looping
      3. Logic
  */
  for (var i = 0; i < arr.length; i++) {
  	arr[i] *= arr[i];
  }
  return arr;
}

var a = [1, 2, 3, 4, 5];
console.log(imperativeSquare(a)); // [1, 4, 9, 16, 25]

predicate-1.js

'use strict';

function predicate() {
  var newReleases = [{
    "id": 70111470,
    "title": "Die Hard",
    "rating": 4.0
  }, {
    "id": 654356453,
    "title": "Bad Boys",
    "rating": 5.0
  }, {
    "id": 65432445,
    "title": "The Chamber",
    "rating": 4.0
  }, {
    "id": 675465,
    "title": "Fracture",
    "rating": 5.0
  }];

  var result = [];

  newReleases.forEach(function(video) {
    return video.rating === 5.0 ? result.push(video) : null;
  });
  return result;
}

console.log(predicate());
/*
[
  {id: 654356453, title: "Bad Boys"}, 
  {id: 675465, title: "Fracture"}
]
*/

predicate-2.js

'use strict';

Array.prototype.filter = function(Predicate) {
  var result = [];

  this.forEach(function(itemInArray) {
    Predicate(itemInArray) ? result.push(itemInArray) : null;
  });

  return result;
}

console.log([1, 2, 3, 4, 5].filter(i => i > 3)); // [4, 5]

predicate-3.js

'use strict';

function predicate() {
  var newReleases = [{
    "id": 70111470,
    "title": "Die Hard",
    "rating": 4.0
  }, {
    "id": 654356453,
    "title": "Bad Boys",
    "rating": 5.0
  }, {
    "id": 65432445,
    "title": "The Chamber",
    "rating": 4.0
  }, {
    "id": 675465,
    "title": "Fracture",
    "rating": 5.0
  }];

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

console.log(predicate());
/*
[
  {id: 654356453, title: "Bad Boys"}, 
  {id: 675465, title: "Fracture"}
]
*/

projection-1.js

'use strict';

function projection() {
  var newReleases = [{
      "id": 70111470,
      "title": "Die Hard",
      "rating": [4.0]
    }, {
      "id": 654356453,
      "title": "Bad Boys",
      "rating": [5.0]
    }, {
      "id": 65432445,
      "title": "The Chamber",
      "rating": [4.0]
    }, {
      "id": 675465,
      "title": "Fracture",
      "rating": [5.0]
    }],
    videoAndTitlePairs = [];

  newReleases.forEach(function(video) {
    videoAndTitlePairs.push({
      id: video.id,
      title: video.title
    });
  });

  return videoAndTitlePairs;
}

console.log(projection());
/*
[{id: 10111470, title: "Die Hard"}, 
{id: 654356453, title: "Bad Boys"}, 
{id: 65432445, title: "The Chamber"},
{id: 675465, title: "Fracture"}
]
*/

projection-2.js

'use strict';

Array.prototype.map = function(projectionFunction) {
  var results = [];
  this.forEach(function(itemInArray) {
    results.push(projectionFunction(itemInArray));

  });

  return results;
};

console.log([1, 2, 3].map(i => i * i)); // [1, 4, 9]

projection-3.js

'use strict';

function projection() {
  var newReleases = [{
      "id": 70111470,
      "title": "Die Hard",
      "rating": [4.0]
    }, {
      "id": 654356453,
      "title": "Bad Boys",
      "rating": [5.0]
    }, {
      "id": 65432445,
      "title": "The Chamber",
      "rating": [4.0]
    }, {
      "id": 675465,
      "title": "Fracture",
      "rating": [5.0]
    }];

  return newReleases.map( release => ({ 
      id: release['id'], 
      title: release['title'] 
    })
  );
}

console.log(projection());
/*
[{id: 10111470, title: "Die Hard"}, 
{id: 654356453, title: "Bad Boys"}, 
{id: 65432445, title: "The Chamber"},
{id: 675465, title: "Fracture"}
]
*/

query-1.js

'use strict';

function queryNestedArray() {
  var movieLists = [{
      name: "New Releases",
      videos: [{
        "id": 70111470,
        "title": "Die Hard",
        "rating": 4.0
      }, {
        "id": 654356453,
        "title": "Bad Boys",
        "rating": 5.0
      }]
    }, {
      name: "Dramas",
      videos: [{
        "id": 65432445,
        "title": "The Chamber",
        "rating": 4.0
      }, {
        "id": 675465,
        "title": "Fracture",
        "rating": 5.0
      }]
    }],
    allVideoIdsInMovieLists = [];

  movieLists.forEach(function(movieList) {
    return movieList.videos.forEach(function(video) {
      return allVideoIdsInMovieLists.push(video.id);
    });
  });

  return allVideoIdsInMovieLists;
}

console.log(queryNestedArray()); // [70111470, 654356453, 65432445, 675465]

query-2.js

'use strict';

Array.prototype.concatAll = function() {
  var results = [];
  this.forEach(function(subArray) {
    if (Array.isArray(subArray))
      subArray.forEach((item) => results.push(item))
    else
      throw new Error('Its not two dimensional array;');
  });

  return results;
};


function queryNestedArray() {
  var movieLists = [{
      name: "New Releases",
      videos: [{
        "id": 70111470,
        "title": "Die Hard",
        "rating": 4.0
      }, {
        "id": 654356453,
        "title": "Bad Boys",
        "rating": 5.0
      }]
    }, {
      name: "Dramas",
      videos: [{
        "id": 65432445,
        "title": "The Chamber",
        "rating": 4.0
      }, {
        "id": 675465,
        "title": "Fracture",
        "rating": 5.0
      }]
    }],
    allVideoIdsInMovieLists = [];

  return movieLists.map(movieList =>
      movieList.videos.map(video =>
        video.id
      ) // [id, id]
    ) // [[id, id], [id, id]]
    .concatAll(); // [id, id, id, id]
}

console.log(queryNestedArray()); // [70111470, 654356453, 65432445, 675465]

reduce-1.js

'use strict';

function reduce() {
  var boxarts = [{
      width: 200,
      height: 200
    }, {
      width: 150,
      height: 200
    }, {
      width: 300,
      height: 200
    }, {
      width: 425,
      height: 150
    }],
    currentSize,
    maxSize = -1,
    largestBoxart;

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

  return largestBoxart;
}

console.log(reduce()); // {width: 425, height: 150}

reduce-2.js

'use strict';

Array.prototype.reduce = function(callback, initialValue) {
  let counter;
  let accumulatedValue;

  if (this.length === 0) {
    return this;
  } else {
    if (arguments.length === 1) {
      counter = 1;
      accumulatedValue = this[0];
    } else if (arguments.length == 2) {
      counter = 0;
      accumulatedValue = initialValue;
    } else {
      throw 'Invalid number of arguments were passed.'
    }
  }

  while (counter < this.length) {
    accumulatedValue = callback(accumulatedValue, this[counter]);
    counter++;
  }

  return [accumulatedValue];
};

console.log([1, 2, 3].reduce(function(p, c) {
  return p + c;
})); // [6]

console.log([1, 2, 3, 4, 5].reduce(function(p, c) {
  return p > c ? p : c;
})); // [5]


var boxarts = [
  { width: 200, height:200 },
  { width: 150, height:200 },
  { width: 300, height:200 },
  { width: 425, height:150 }
];

console.log(boxarts.reduce(function(p, c) {
	return p.width * p.height > c.width * c.height ? p : c; 
})); // [{height: 150, width: 425}]
		

traverse-1.js

'use strict';

function traverse() {
  let names = ["Apple", "Microsoft", "Facebook", "Linkedin"];

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

traverse(); // Apple, Microsoft, Facebook, Linkedin

traverse.js

'use strict';

function traverse() {
  let names = ["Apple", "Microsoft", "Facebook", "Linkedin"],
    counter;

  for (counter = 0; counter < names.length; counter++) {
    console.log(names[counter]);
  }
};

traverse(); // Apple, Microsoft, Facebook, Linkedin

zip-1.js

'use strict';

function zip() {
  var videos = [{
      "id": 70111470,
      "title": "Die Hard",
      "rating": 4.0,
    }, {
      "id": 654356453,
      "title": "Bad Boys",
      "rating": 5.0,
    }, {
      "id": 65432445,
      "title": "The Chamber",
      "rating": 4.0,
    }, {
      "id": 675465,
      "title": "Fracture",
      "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++) {
    videoIdAndBookmarkIdPairs.push({
      videoId: videos[counter].id,
      bookmarkId: bookmarks[counter].id
    });
  }

  return videoIdAndBookmarkIdPairs;
}

console.log(zip());
/* 
  [
    {bookmarkId: 470, videoId: 70111470}, 
    {bookmarkId: 453, videoId: 654356453}, 
    {bookmarkId: 445, videoId: 65432445}
  ]
*/

zip-2.js

'use strict';

Array.prototype.zip = function(left, right, combinerFunction) {
  let results, length;

  length = Math.min(left.length, right.length);
	results = [];
  for (let i = 0; i < length; i++) {
    results.push(combinerFunction(left[i], right[i]));
  }

  return results;
}

console.log([].zip([1, 2], [1, 2, 3], function(l, r) {
	return l + r; 
})); // [2, 4]

zip-3.js

'use strict';


Array.prototype.zip = function(left, right, combinerFunction) {
  let results, length;

  length = Math.min(left.length, right.length);
  results = [];
  for (let i = 0; i < length; i++) {
    results.push(combinerFunction(left[i], right[i]));
  }

  return results;
}

function zip() {
  var videos = [{
      "id": 70111470,
      "title": "Die Hard",
      "rating": 4.0
    }, {
      "id": 654356453,
      "title": "Bad Boys",
      "rating": 5.0
    }, {
      "id": 65432445,
      "title": "The Chamber",
      "rating": 4.0
    }, {
      "id": 675465,
      "title": "Fracture",
      "rating": 5.0
    }],
    bookmarks = [{
      id: 470,
      time: 23432
    }, {
      id: 453,
      time: 234324
    }, {
      id: 445,
      time: 987834
    }];

  return Array.prototype.zip(videos, bookmarks, function(l, r) {
    return {
      videoId: l.id,
      bookmarkId: r.id
    };
  });
}

console.log(zip());
/* 
  [
    {bookmarkId: 470, videoId: 70111470}, 
    {bookmarkId: 453, videoId: 654356453}, 
    {bookmarkId: 445, videoId: 65432445}
  ]
*/