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>
120 lines
2.9 KiB
Markdown
120 lines
2.9 KiB
Markdown
---
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id: 5a24c314108439a4d4036172
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title: 以另一种方式在用户界面中渲染状态
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challengeType: 6
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forumTopicId: 301408
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dashedName: render-state-in-the-user-interface-another-way
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---
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# --description--
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还有另一种方法可以访问组件中的`state`。在`render()`方法中，在`return`语句之前，你可以直接编写 JavaScript。例如，你可以声明函数、从`state`或`props`访问数据、对此数据执行计算等。然后，你可以将任何数据赋值给你在`return`语句中可以访问的变量。
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# --instructions--
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在`MyComponent`的 render 方法中，定义一个名为`name`的`常量`，并将其设置为组件`state`中的 name 值。因为可以直接在代码部分编写 JavaScript，所以不需要用大括号括起来。
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接下来，在 return 语句中，在`h1`标签中渲染变量`name`的值。记住，在 return 语句中需要使用 JSX 语法（用到 JavaScript 的花括号）。
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# --hints--
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`MyComponent`应该有一个键`name`，其值`freeCodeCamp`存储在其 state 中。
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```js
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assert(
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Enzyme.mount(React.createElement(MyComponent)).state('name') ===
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'freeCodeCamp'
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);
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```
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`MyComponent`应该在`div`中渲染一个`h1`标题。
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```js
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assert(
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/<div><h1>.*<\/h1><\/div>/.test(
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Enzyme.mount(React.createElement(MyComponent)).html()
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)
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);
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```
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渲染的`h1`标签应该包含`{name}`的引用。
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```js
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(getUserInput) =>
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assert(/<h1>\n*\s*\{\s*name\s*\}\s*\n*<\/h1>/.test(getUserInput('index')));
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```
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渲染的`h1`标题中应该包含一段文本，这段文本是从组件的 state 中渲染出来的。
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```js
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async () => {
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const waitForIt = (fn) =>
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new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250));
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const mockedComponent = Enzyme.mount(React.createElement(MyComponent));
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const first = () => {
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mockedComponent.setState({ name: 'TestName' });
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return waitForIt(() => mockedComponent.html());
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};
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const firstValue = await first();
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assert(firstValue === '<div><h1>TestName</h1></div>');
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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(<MyComponent />, document.getElementById('root'))
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```
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## --seed-contents--
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```jsx
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class MyComponent 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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// Change code below this line
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// Change code above this line
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return (
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<div>
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{ /* Change code below this line */ }
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{ /* Change code above this line */ }
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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 MyComponent 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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// Change code below this line
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const name = this.state.name;
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// Change code above this line
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return (
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<div>
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{ /* Change code below this line */ }
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<h1>{name}</h1>
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{ /* Change code above this line */ }
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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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