ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
117 lines
3.2 KiB
Markdown
117 lines
3.2 KiB
Markdown
---
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id: 5a24c314108439a4d4036157
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title: 用 Redux 写一个计数器
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challengeType: 6
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forumTopicId: 301453
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dashedName: write-a-counter-with-redux
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---
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# --description--
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现在你已经了解了 Redux 的所有核心原则！你已经了解了如何创建 action 和 action creator，创建 Redux store，通过 store dispatch action，以及使用纯粹的 reducer 设计状态更新。你甚至已经看到过如何使用 reducer 组合管理复杂状态并处理异步操作。这些例子很简单，但这些概念是 Redux 的核心原则。如果你理解它们，你就可以开始构建自己的 Redux 应用了。接下来的挑战包括关于`state`不变性的一些细节，但是，这里是对你到目前为止学到的所有内容的回顾。
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# --instructions--
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在本课程中，你将从头开始使用 Redux 实现一个简单的计数器。基本知识在代码编辑器中提供，但你必须完成详细的内容！使用提供给你的名称并定义`incAction`和`decActio` action creator `counterReducer()`，`INCREMENT`和`DECREMENT` action 类型，最后是 Redux `store`。一旦完成，你应该能够 dispatch `INCREMENT`或`DECREMENT`动作来增加或减少`store`中保存的状态。开始构建你的第一个 Redux 应用程序吧，祝你好运！
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# --hints--
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action creator `incAction`应返回一个 action 对象 {type:"INCREMENT"}。
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```js
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assert(incAction().type === INCREMENT);
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```
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action creator `decAction`应返回一个 action 对象 {type:"DECREMENT"}。
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```js
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assert(decAction().type === DECREMENT);
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```
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Redux store 应该将`state`初始化为 0。
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```js
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assert(store.getState() === 0);
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```
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在 Redux store 上 dispatch `incAction`应该将`state`增加 1。
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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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store.dispatch(incAction());
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const incState = store.getState();
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return initialState + 1 === incState;
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})()
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);
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```
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在 Redux store 上 dispatch `decAction`应该将`state`减少 1。
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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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store.dispatch(decAction());
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const decState = store.getState();
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return initialState - 1 === decState;
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})()
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);
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```
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`counterReducer`必须是一个函数。
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```js
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assert(typeof counterReducer === 'function');
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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 INCREMENT = null; // Define a constant for increment action types
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const DECREMENT = null; // Define a constant for decrement action types
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const counterReducer = null; // Define the counter reducer which will increment or decrement the state based on the action it receives
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const incAction = null; // Define an action creator for incrementing
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const decAction = null; // Define an action creator for decrementing
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const store = null; // Define the Redux store here, passing in your reducers
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```
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# --solutions--
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```js
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const INCREMENT = 'INCREMENT';
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const DECREMENT = 'DECREMENT';
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const counterReducer = (state = 0, action) => {
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switch(action.type) {
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case INCREMENT:
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return state + 1;
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case DECREMENT:
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return state - 1;
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default:
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return state;
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}
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};
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const incAction = () => {
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return {
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type: INCREMENT
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}
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};
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const decAction = () => {
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return {
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type: DECREMENT
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}
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};
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const store = Redux.createStore(counterReducer);
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```
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