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2018-10-12 15:37:13 -04:00
---
title: Refactor Global Variables Out of Functions
---
# Refactor Global Variables Out of Functions
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---
## Hints
### Hint 1
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- If you're having trouble with changing bookList, try using a copy of the array in your functions.
### Hint 2
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- Here's some more information about [how JavaScript handles function arguments](https://codeburst.io/javascript-passing-by-value-vs- reference-explained-in-plain-english-8d00fd06a47c).
---
## Solutions
<details><summary>Solution 1 (Click to Show/Hide)</summary>
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```javascript
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.
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return newArr; // Return the new array.
}
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.
//.
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newArr.splice(newArr.indexOf(bookName), 1); // Remove the given paramater from the new array.
return newArr; // Return the new array.
}
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}
```
</details>
<details><summary>Solution 2 (Click to Show/Hide)</summary>
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```javascript
function add(list, bookName) {
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return [...list, bookName];
}
function remove(list, bookName) {
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if (list.indexOf(bookName) >= 0) {
return list.filter(item => item !== bookName);
}
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}
```
</details>