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>
88 lines
2.3 KiB
Markdown
88 lines
2.3 KiB
Markdown
---
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id: 5a24c314108439a4d403617c
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title: 使用生命周期方法：componentWillMount
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challengeType: 6
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forumTopicId: 301423
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dashedName: use-the-lifecycle-method-componentwillmount
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---
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# --description--
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React 组件有几种特殊方法，可以在组件生命周期的特定点执行操作。这些称为生命周期方法或生命周期钩子，允许你在特定时间点捕获组件。这可以在渲染之前、更新之前、接收 props 之前、卸载之前等等。以下是一些主要生命周期方法的列表： `componentWillMount()` `componentDidMount()` `shouldComponentUpdate()` `componentDidUpdate()` `componentWillUnmount()` 接下来的几节课将讲述这些生命周期方法的一些基本用例。
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**注意：** `componentWillMount` 生命周期方法会在版本 16.X 废弃在版本 17 移除 [(Source)](https://reactjs.org/blog/2018/03/27/update-on-async-rendering.html)
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# --instructions--
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当组件被挂载到 DOM 时，`componentWillMount()`方法在`render()`方法之前被调用。在`componentWillMount()`中将一些内容记录到控制台--你需要打开浏览器控制台以查看输出。
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# --hints--
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`MyComponent`应该渲染一个`div`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(React.createElement(MyComponent));
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return mockedComponent.find('div').length === 1;
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})()
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);
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```
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应该在`componentWillMount`中调用`console.log`。
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```js
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assert(
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(function () {
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const lifecycle = React.createElement(MyComponent)
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.type.prototype.componentWillMount.toString()
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.replace(/ /g, '');
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return lifecycle.includes('console.log(');
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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(<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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}
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componentWillMount() {
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// Change code below this line
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// Change code above this line
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}
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render() {
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return <div />
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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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}
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componentWillMount() {
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// Change code below this line
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console.log('Component is mounting...');
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// Change code above this line
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}
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render() {
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return <div />
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}
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};
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```
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