Refactor Global Variables Out of Functions - error

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What is wrong in my code?

Your code so far


// 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 the bookName one

// Add your code below this line
function add (arr, bookName) {
  let newArr = [...arr];
  bookList.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 newArr = [...arr];
  if (newArr.indexOf(bookName) >= 0) {
      newArr.splice(newArr.indexOf(bookName), 1);
    return newArr;
    
    // 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);



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Link to the challenge:
https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/functional-programming/refactor-global-variables-out-of-functions/

You are making a local copy of the array, but then changing the global variable, and returning the unmutated local variable…