80 lines
3.6 KiB
Markdown
80 lines
3.6 KiB
Markdown
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---
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id: 5a24c314108439a4d403615b
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title: Copy an Object with Object.assign
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challengeType: 6
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isRequired: false
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videoUrl: ''
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localeTitle: 使用Object.assign复制对象
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---
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## Description
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<section id="description">最后几个挑战适用于数组，但是当状态是一个<code>object</code>时，有一些方法可以帮助强制执行状态不变性。处理对象的有用工具是<code>Object.assign()</code>实用程序。 <code>Object.assign()</code>接受目标对象和源对象，并将源对象中的属性映射到目标对象。任何匹配的属性都会被源对象中的属性覆盖。此行为通常用于通过将空对象作为第一个参数传递，然后传递要复制的对象来生成对象的浅副本。这是一个例子： <code>const newObject = Object.assign({}, obj1, obj2);</code>这将<code>newObject</code>创建为一个新<code>object</code> ，其中包含当前存在于<code>obj1</code>和<code>obj2</code>中的属性。 </section>
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## Instructions
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<section id="instructions"> Redux状态和操作被修改为处理<code>state</code>的<code>object</code> 。编辑代码以返回类型为<code>ONLINE</code>操作的新<code>state</code>对象，该<code>status</code>属性将<code>status</code>属性设置为<code>online</code>字符串。尝试使用<code>Object.assign()</code>来完成挑战。 </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存储应该存在并使用等效于第1行声明的<code>defaultState</code>对象的状态进行初始化。
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testString: 'assert((function() { const expectedState = { user: "CamperBot", status: "offline", friends: "732,982", community: "freeCodeCamp" }; const initialState = store.getState(); return DeepEqual(expectedState, initialState); })(), "The Redux store should exist and initialize with a state that is equivalent to the <code>defaultState</code> object declared on line 1.");'
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- text: <code>wakeUp</code>和<code>immutableReducer</code>都应该是函数。
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testString: 'assert(typeof wakeUp === "function" && typeof immutableReducer === "function", "<code>wakeUp</code> and <code>immutableReducer</code> both should be functions.");'
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- text: 调度<code>ONLINE</code>类型的操作应该将<code>status</code>中的属性<code>status</code>更新为<code>online</code>并且不应该改变状态。
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testString: 'assert((function() { const initialState = store.getState(); const isFrozen = DeepFreeze(initialState); store.dispatch({type: "ONLINE"}); const finalState = store.getState(); const expectedState = { user: "CamperBot", status: "online", friends: "732,982", community: "freeCodeCamp" }; return isFrozen && DeepEqual(finalState, expectedState); })(), "Dispatching an action of type <code>ONLINE</code> should update the property <code>status</code> in state to <code>online</code> and should NOT mutate state.");'
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- text: <code>Object.assign</code>应该用于返回新状态。
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testString: 'getUserInput => assert(getUserInput("index").includes("Object.assign"), "<code>Object.assign</code> should be used to return new 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 defaultState = {
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user: 'CamperBot',
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status: 'offline',
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friends: '732,982',
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community: 'freeCodeCamp'
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};
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const immutableReducer = (state = defaultState, action) => {
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switch(action.type) {
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case 'ONLINE':
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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 wakeUp = () => {
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return {
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type: 'ONLINE'
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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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