[beta] Bug in seed code for "Functional Programming: Refactor Global Variables Out of Functions"

Challenge refactor-global-variables-out-of-functions has an issue.

According to the instructions, the goal of this challenge is to

Refactor (rewrite) the code so the global array bookList is not changed inside either function.

Another requirement (which doesn’t seem to be be tested for) is that

Both functions should return an array

The problem is that the initial challengeSeed doesn’t meet the second requirement since neither Array.push() nor Array.splice() returns the updated array. Since the challenge’s intention seems to be to “Refactor Global Variables Out of Functions”, I think this needs to be fixed, so campers can focus on removing global variables rather than making the code work.

To resolve these issues, I think we should

• Make sure the functions in the challengeSeed returns the updated array, as their doc strings says.
• Possibly add tests to verify that the functions do return an array.

// 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 (bookName) {
  
  return bookList.push(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 (bookName) {
  if (bookList.indexOf(bookName) >= 0) {
    
    return bookList.splice(0, 1, bookName);
    
    // 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);

[Greenheart]

I really like the idea of only using local variables in functions, but it feels like this challenge is trying to do too much at one time.

Maybe we could split the concepts into two smaller challenges:

1. Refactor Global Variables out of Functions

• Use similar challengeSeed to what we have now.
• The goal is to replace the global variable bookList with a function-parameter (that campers decide the name for).

2. Avoid Mutating External Variables

• Builds upon the challengeSeed from the previous challenge.
• The goal is to teach why and how to avoid modifying variables you get passed to your functions.
• In this case, this could be about using Array.prototype.slice() to create a copy before changing any data in the array with books.

What do you think? 😊

[BurnhamG]

I’ve been working on fixing this and should have a pull request in by early next week at the very latest.

On Wed, Oct 17, 2018, 17:25 Rabindranath Ferreira [e-mail] wrote:

any advance with this i try 2 solutions using local variables inside off function and does’t work, and when i try to use slice or indexOf method for arrays the console told me “this xxxx is not a function”

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