79d9012432
* fix(curriculum): tests quotes * fix(curriculum): fill seed-teardown * fix(curriculum): fix tests and remove unneeded seed-teardown
94 lines
2.9 KiB
Markdown
94 lines
2.9 KiB
Markdown
---
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id: 5a24c314108439a4d403615a
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title: Remove an Item from an Array
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challengeType: 6
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isRequired: false
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---
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## Description
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<section id='description'>
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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>.
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</section>
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## Instructions
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<section id='instructions'>
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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.
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: The Redux store should exist and initialize with a state equal to <code>[0,1,2,3,4,5]</code>
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testString: assert((function() { const initialState = store.getState(); return (Array.isArray(initialState) === true && DeepEqual(initialState, [0, 1, 2, 3, 4, 5])); })(), 'The Redux store should exist and initialize with a state equal to <code>[0,1,2,3,4,5]</code>');
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- text: <code>removeItem</code> and <code>immutableReducer</code> both should be functions.
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testString: assert(typeof removeItem === 'function' && typeof immutableReducer === 'function', '<code>removeItem</code> and <code>immutableReducer</code> both should be functions.');
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- text: Dispatching the <code>removeItem</code> action creator should remove items from the state and should NOT mutate state.
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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]); })(), 'Dispatching the <code>removeItem</code> action creator should remove items from the state and should NOT mutate state.');
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='jsx-seed'>
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```jsx
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const immutableReducer = (state = [0,1,2,3,4,5], action) => {
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switch(action.type) {
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case 'REMOVE_ITEM':
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// don't mutate state here or the tests will fail
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return
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default:
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return state;
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}
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};
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const removeItem = (index) => {
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return {
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type: 'REMOVE_ITEM',
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index
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}
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}
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const store = Redux.createStore(immutableReducer);
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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const immutableReducer = (state = [0,1,2,3,4,5], action) => {
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switch(action.type) {
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case 'REMOVE_ITEM':
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return [
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...state.slice(0, action.index),
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...state.slice(action.index + 1)
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];
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default:
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return state;
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}
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};
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const removeItem = (index) => {
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return {
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type: 'REMOVE_ITEM',
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index
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}
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}
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const store = Redux.createStore(immutableReducer);
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```
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</section>
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