Change:
<!-- NOTE: If you're reporting a security issue, don't create a GitHub issue. Instead, email We will look into it immediately. -- This is the starter code: The starter code for this challenge is strange. 1) Why the space between the function name and the ()s for the arguments? 2) I get that the idea is to have the learners change the function signature, but it is a bit strange having a mismatch between the function signatures and the function calls in the starter code.
The linked PR in this issue. For , we could probably move away from having variables in the seed code and instead assert the function returns the expected value

Discussion:
`bookList` should not change and still equal `["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]`. ```js <ins> add(bookList, "Test"); </ins> assert( JSON.stringify(bookList) === JSON.stringify([

); ``` <del> `newBookList` should equal `["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]`. </del> <ins> `add(bookList, "A Brief History of Time")` should return `["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]`. </ins> ```js assert( <del> JSON.stringify(newBookList) === </del> <ins> JSON.stringify(add(bookList, "A Brief History of Time")) === </ins> JSON.stringify([ 'The Hound of the Baskervilles', 'On The Electrodynamics of Moving Bodies',

); ``` <del> `newerBookList` should equal `["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]`. </del> <ins> `remove(bookList, "On The Electrodynamics of Moving Bodies")` should return `["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]`. </ins> ```js assert( <del> JSON.stringify(newerBookList) === </del> <ins> JSON.stringify(remove(bookList, 'On The Electrodynamics of Moving Bodies')) === </ins> JSON.stringify([ 'The Hound of the Baskervilles', 'Philosophiæ Naturalis Principia Mathematica',

); ``` <del> `newestBookList` should equal `["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]`. </del> <ins> `remove(add(bookList, "A Brief History of Time"), "On The Electrodynamics of Moving Bodies");` should equal `["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]`. </ins> ```js assert( <del> JSON.stringify(newestBookList) === </del> <ins> JSON.stringify(remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies')) === </ins> JSON.stringify([ 'The Hound of the Baskervilles', 'Philosophiæ Naturalis Principia Mathematica',

// Change code above this line } } <del> const newBookList = add(bookList, 'A Brief History of Time'); const newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies'); const newestBookList = remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies'); console.log(bookList); </del> ``` # --solutions--

} return bookListCopy; } <del> const newBookList = add(bookList, 'A Brief History of Time'); const newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies'); const newestBookList = remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies'); </del> ```