115 lines
2.5 KiB
Markdown
115 lines
2.5 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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forumTopicId: 301447
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dashedName: remove-an-item-from-an-array
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---
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# --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 `slice()` and `concat()`.
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# --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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# --hints--
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The Redux store should exist and initialize with a state equal to `[0,1,2,3,4,5]`
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```js
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assert(
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(function () {
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const initialState = store.getState();
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return (
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Array.isArray(initialState) === true &&
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DeepEqual(initialState, [0, 1, 2, 3, 4, 5])
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);
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})()
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);
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```
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`removeItem` and `immutableReducer` both should be functions.
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```js
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assert(
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typeof removeItem === 'function' && typeof immutableReducer === 'function'
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);
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```
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Dispatching the `removeItem` action creator should remove items from the state and should NOT mutate state.
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```js
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assert(
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(function () {
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const initialState = store.getState();
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const isFrozen = DeepFreeze(initialState);
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store.dispatch(removeItem(3));
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const state_1 = store.getState();
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store.dispatch(removeItem(2));
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const state_2 = store.getState();
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store.dispatch(removeItem(0));
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store.dispatch(removeItem(0));
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store.dispatch(removeItem(0));
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const state_3 = store.getState();
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return (
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isFrozen &&
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DeepEqual(state_1, [0, 1, 2, 4, 5]) &&
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DeepEqual(state_2, [0, 1, 4, 5]) &&
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DeepEqual(state_3, [5])
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);
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})()
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);
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```
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# --seed--
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## --seed-contents--
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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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// 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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# --solutions--
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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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