freeCodeCamp Challenge Guide: Refactor Global Variables Out of Functions

Guide
1

Refactor Global Variables Out of Functions

Hints

Hint 1

  • If you’re having trouble with changing bookList, try using a copy of the array in your functions.

Hint 2

Solutions

Solution 1 (Click to Show/Hide) 
// 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]; // Copy the bookList array to a new array.
  newArr.push(bookName); // Add bookName parameter to the end of the new array.
  return newArr; // Return the new array.
}

/* 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 newArr = [...arr]; // Copy the bookList array to a new array.
  if (newArr.indexOf(bookName) >= 0) {
    // Check whether the bookName parameter is in new array.
    newArr.splice(newArr.indexOf(bookName), 1); // Remove the given paramater from the new array.
    return newArr; // Return the new array.
  }
}

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);
Solution 2 (Click to Show/Hide) 
// 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

function add(list, bookName) {
  return [...list, bookName];
}

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

function remove(list, bookName) {
  return list.filter(book => book !== 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);
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