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>
135 lines
3.3 KiB
Markdown
135 lines
3.3 KiB
Markdown
---
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id: 5a24c314108439a4d4036170
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title: 创建一个有状态的组件
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challengeType: 6
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forumTopicId: 301391
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dashedName: create-a-stateful-component
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---
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# --description--
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React中最重要的主题之一是`state`。 state 包含应用程序需要了解的任何数据，这些数据可能会随时间而变化。你希望应用程序能够响应 state 的变更，并在必要时显示更新后的 UI。React 为现代 Web 应用程序的状态管理提供了一个很好的解决方案。
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你可以通过在`constructor`中的组件类上声明`state`属性来在 React 组件中创建 state，它在创建时使用`state`初始化组件。`state`属性必须设置为 JavaScript`对象`。声明如下：
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```jsx
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this.state = {
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// describe your state here
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}
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```
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你可以在组件的整个生命周期内访问`state`对象，你可以更新它、在 UI 中渲染它，也可以将其作为 props 传递给子组件。`state`对象的使用可以很简单，亦可以很复杂，就看你怎么用了。请注意，你必须通过扩展`React.Component`来创建类组件，以便像这样创建`state`。
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# --instructions--
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代码编辑器中有一个组件试图从其`state`中渲染一个`name`属性，但是`state`还没有定义。在`constructor`中使用`state`初始化组件，并将你的名字赋给`name`属性。
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# --hints--
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`StatefulComponent`应该存在并被渲染。
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```js
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(
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React.createElement(StatefulComponent)
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);
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return mockedComponent.find('StatefulComponent').length === 1;
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})()
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);
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```
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`StatefulComponent`应该渲染一个`div`元素和一个`h1`元素。
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```js
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(
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React.createElement(StatefulComponent)
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);
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return (
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mockedComponent.find('div').length === 1 &&
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mockedComponent.find('h1').length === 1
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);
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})()
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);
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```
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应使用被设置为字符串的`name`属性来初始化`StatefulComponent`的 state。
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```js
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(
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React.createElement(StatefulComponent)
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);
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const initialState = mockedComponent.state();
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return (
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typeof initialState === 'object' && typeof initialState.name === 'string'
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);
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})()
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);
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```
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`StatefulComponent`中 state 的`name`属性应该渲染在`h1`元素里。
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```js
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(
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React.createElement(StatefulComponent)
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);
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const initialState = mockedComponent.state();
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return mockedComponent.find('h1').text() === initialState.name;
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})()
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);
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```
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# --seed--
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## --after-user-code--
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```jsx
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ReactDOM.render(<StatefulComponent />, document.getElementById('root'))
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```
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## --seed-contents--
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```jsx
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class StatefulComponent extends React.Component {
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constructor(props) {
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super(props);
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// Only change code below this line
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// Only change code above this line
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}
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render() {
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return (
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<div>
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<h1>{this.state.name}</h1>
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</div>
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);
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}
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};
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```
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# --solutions--
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```jsx
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class StatefulComponent extends React.Component {
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constructor(props) {
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super(props);
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this.state = {
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name: 'freeCodeCamp!'
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}
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}
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render() {
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return (
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<div>
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<h1>{this.state.name}</h1>
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</div>
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);
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}
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};
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```
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