<section id="description">
<p>До сих пор мы видели два разных принципа функционального программирования: 1) Не изменяйте переменную или объект - создавайте новые переменные и объекты и возвращайте их, если необходимо, из функции. 2) Объявлять аргументы функции - любое вычисление внутри функции зависит только от аргументов, а не от любого глобального объекта или переменной. Добавление одного к числу не очень интересно, но мы можем применять эти принципы при работе с массивами или более сложными объектами.</p></section>

// the global variable
var bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];

/* This function should add a book to the list and return the list */
// New parameters should come before bookName

// Add your code below this line
function add (bookName) {

  bookList.push(bookName);
  return bookList;
  
  // Add your code above this line
}

/* This function should remove a book from the list and return the list */
// New parameters should come before the bookName one

// Add your code below this line
function remove (bookName) {
  var book_index = bookList.indexOf(bookName);
  if (book_index >= 0) {

    bookList.splice(book_index, 1);
    return bookList;

    // Add your code above this line
    }
}

var newBookList = add(bookList, 'A Brief History of Time');
var newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies');
var newestBookList = remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies');

console.log(bookList);


index

Глобальные переменные Refactor вне функций

Refactor Global Variables Out of Functions

<code>bookList</code> should not change and still equal <code>["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]</code>.

<code>newBookList</code> should equal <code>["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]</code>.

<code>newerBookList</code> should equal <code>["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]</code>.

<code>newestBookList</code> should equal <code>["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]</code>.

javascript-algorithms-and-data-structures

Functional Programming

// the global variable
var bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];

/* This function should add a book to the list and return the list */
// New parameters should come before bookName

// Add your code below this line
function add (bookList, bookName) {
    return [...bookList, bookName];
}

/* This function should remove a book from the list and return the list */
// New parameters should come before the bookName one

function remove (bookList, bookName) {
    var book_index = bookList.indexOf(bookName);
    if (book_index >= 0) {
        return new Array(...bookList.slice(0, book_index), ...bookList.slice(book_index + 1));
    }
}

var newBookList = add(bookList, 'A Brief History of Time');
var newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies');
var newestBookList = remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies');

console.log(bookList);
console.log(newBookList);


// the global variable
var bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];

/* This function should add a book to the list and return the list */
// New parameters should come before bookName

// Add your code below this line
function add (arr,bookName) {
let newArr = [...arr];
  newArr.push(bookName);
  return newArr;
  
  // Add your code above this line
}

/* This function should remove a book from the list and return the list */
// New parameters should come before the bookName one

// Add your code below this line
function remove (arr,bookName) {
  let newerArr = [...arr];
  var book_index = newerArr.indexOf(bookName);
  if (book_index >= 0) {

    newerArr.splice(book_index, 1);
    return newerArr;

    // Add your code above this line
    }
}

var newBookList = add(bookList, 'A Brief History of Time');
var newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies');
var newestBookList = remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies');

console.log(bookList);


// the global variable
var bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];

/* This function should add a book to the list and return the list */
// New parameters should come before bookName

// Add your code below this line
function add(list, bookName) {

  return [...list, bookName];

  // Add your code above this line
}

/* This function should remove a book from the list and return the list */
// New parameters should come before the bookName one

// Add your code below this line
function remove(list, bookName) {
  return list.filter(item => item !== bookName);
}

var newBookList = add(bookList, 'A Brief History of Time');
var newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies');
var newestBookList = remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies');

console.log(bookList);


// the global variable
var bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];

/* This function should add a book to the list and return the list */
// New parameters should come before bookName

// Add your code below this line
function add (arg, bookName) {
  let arr = arg.slice(0);
  arr.push(bookName);
  return arr;
  
  // Add your code above this line
}

/* This function should remove a book from the list and return the list */
// New parameters should come before the bookName one

// Add your code below this line
function remove (arg, bookName) {
  let arr = [...arg];
  var book_index = arr.indexOf(bookName);
  if (book_index >= 0) {

    arr.splice(book_index, 1);
    return arr;

    // Add your code above this line
    }
}

var newBookList = add(bookList, 'A Brief History of Time');
var newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies');
var newestBookList = remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies');

console.log(bookList);


// the global variable
var bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];

/* This function should add a book to the list and return the list */
// New parameters should come before bookName

// Add your code below this line
function add(bookList, bookName) {
  let newBookList = bookList.slice(); // Create a copy of the original array
  newBookList.push(bookName);
  return newBookList;
  // Add your code above this line
}

/* This function should remove a book from the list and return the list */
// New parameters should come before the bookName one

// Add your code below this line
function remove(bookList, bookName) {
  let newBookList = bookList.slice(); // Create a copy of the original array
  var book_index = newBookList.indexOf(bookName);
  if (book_index >= 0) {
    newBookList.splice(book_index, 1);
    return newBookList;

    // Add your code above this line
    }
}

var newBookList = add(bookList, 'A Brief History of Time');
var newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies');
var newestBookList = remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies');

console.log(bookList);
