72 lines
2.5 KiB
Markdown
72 lines
2.5 KiB
Markdown
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---
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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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videoUrl: ''
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localeTitle: 从数组中删除项目
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---
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## Description
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<section id="description">是时候练习从数组中删除项目了。扩展运算符也可以在这里使用。其他有用的JavaScript方法包括<code>slice()</code>和<code>concat()</code> 。 </section>
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## Instructions
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<section id="instructions">修改了reducer和action creator，以根据项目的索引从数组中删除项目。完成编写reducer以便返回一个新的状态数组，并删除特定索引处的项。 </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: 'Redux存储应该存在并初始化为等于<code>[0,1,2,3,4,5]</code>的状态'
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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>和<code>immutableReducer</code>都应该是函数。
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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: 调度<code>removeItem</code>动作创建者应该从状态中删除项目，不应该改变状态。
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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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// solution required
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```
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</section>
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