95 lines
2.7 KiB
Markdown
95 lines
2.7 KiB
Markdown
---
|
|
id: 5a24c314108439a4d403615a
|
|
title: Remove an Item from an Array
|
|
challengeType: 6
|
|
isRequired: false
|
|
forumTopicId: 301447
|
|
---
|
|
|
|
## Description
|
|
<section id='description'>
|
|
Time to practice removing items from an array. The spread operator can be used here as well. Other useful JavaScript methods include <code>slice()</code> and <code>concat()</code>.
|
|
</section>
|
|
|
|
## Instructions
|
|
<section id='instructions'>
|
|
The reducer and action creator were modified to remove an item from an array based on the index of the item. Finish writing the reducer so a new state array is returned with the item at the specific index removed.
|
|
</section>
|
|
|
|
## Tests
|
|
<section id='tests'>
|
|
|
|
```yml
|
|
tests:
|
|
- text: The Redux store should exist and initialize with a state equal to <code>[0,1,2,3,4,5]</code>
|
|
testString: assert((function() { const initialState = store.getState(); return (Array.isArray(initialState) === true && DeepEqual(initialState, [0, 1, 2, 3, 4, 5])); })());
|
|
- text: <code>removeItem</code> and <code>immutableReducer</code> both should be functions.
|
|
testString: assert(typeof removeItem === 'function' && typeof immutableReducer === 'function');
|
|
- text: Dispatching the <code>removeItem</code> action creator should remove items from the state and should NOT mutate state.
|
|
testString: assert((function() { const initialState = store.getState(); const isFrozen = DeepFreeze(initialState); store.dispatch(removeItem(3)); const state_1 = store.getState(); store.dispatch(removeItem(2)); const state_2 = store.getState(); store.dispatch(removeItem(0)); store.dispatch(removeItem(0)); store.dispatch(removeItem(0)); const state_3 = store.getState(); return isFrozen && DeepEqual(state_1, [0, 1, 2, 4, 5]) && DeepEqual(state_2, [0, 1, 4, 5]) && DeepEqual(state_3, [5]); })());
|
|
|
|
```
|
|
|
|
</section>
|
|
|
|
## Challenge Seed
|
|
<section id='challengeSeed'>
|
|
|
|
<div id='jsx-seed'>
|
|
|
|
```jsx
|
|
const immutableReducer = (state = [0,1,2,3,4,5], action) => {
|
|
switch(action.type) {
|
|
case 'REMOVE_ITEM':
|
|
// don't mutate state here or the tests will fail
|
|
return
|
|
default:
|
|
return state;
|
|
}
|
|
};
|
|
|
|
const removeItem = (index) => {
|
|
return {
|
|
type: 'REMOVE_ITEM',
|
|
index
|
|
}
|
|
}
|
|
|
|
const store = Redux.createStore(immutableReducer);
|
|
```
|
|
|
|
</div>
|
|
|
|
|
|
|
|
</section>
|
|
|
|
## Solution
|
|
<section id='solution'>
|
|
|
|
|
|
```js
|
|
const immutableReducer = (state = [0,1,2,3,4,5], action) => {
|
|
switch(action.type) {
|
|
case 'REMOVE_ITEM':
|
|
return [
|
|
...state.slice(0, action.index),
|
|
...state.slice(action.index + 1)
|
|
];
|
|
default:
|
|
return state;
|
|
}
|
|
};
|
|
|
|
const removeItem = (index) => {
|
|
return {
|
|
type: 'REMOVE_ITEM',
|
|
index
|
|
}
|
|
}
|
|
|
|
const store = Redux.createStore(immutableReducer);
|
|
```
|
|
|
|
</section>
|