73 lines
2.4 KiB
Markdown
73 lines
2.4 KiB
Markdown
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---
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id: 5a24c314108439a4d403617c
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title: Use the Lifecycle Method componentWillMount
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challengeType: 6
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isRequired: false
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videoUrl: ''
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localeTitle: 使用生命周期方法componentWillMount
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---
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## Description
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<section id="description"> 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，允许您在特定时间点捕获组件。这可以在渲染之前，更新之前，接收道具之前，卸载之前等等。以下是一些主要生命周期方法的列表： <code>componentWillMount()</code> <code>componentDidMount()</code> <code>componentWillReceiveProps()</code> <code>shouldComponentUpdate()</code> <code>componentWillUpdate()</code> <code>componentDidUpdate()</code> <code>componentWillUnmount()</code>接下来的几节课将介绍这些生命周期方法的一些基本用例。 </section>
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## Instructions
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<section id="instructions">在将组件装载到DOM时，在<code>render()</code>方法之前调用<code>componentWillMount()</code>方法。在<code>componentWillMount()</code>中将某些内容记录到控制台 - 您可能希望打开浏览器控制台以查看输出。 </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: <code>MyComponent</code>应该呈现<code>div</code>元素。
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testString: 'assert((function() { const mockedComponent = Enzyme.mount(React.createElement(MyComponent)); return mockedComponent.find("div").length === 1; })(), "<code>MyComponent</code> should render a <code>div</code> element.");'
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- text: 应该在<code>componentWillMount</code>调用<code>console.log</code> 。
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testString: 'assert((function() { const lifecycle = React.createElement(MyComponent).type.prototype.componentWillMount.toString().replace(/ /g,""); return lifecycle.includes("console.log("); })(), "<code>console.log</code> should be called in <code>componentWillMount</code>.");'
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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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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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</div>
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### After Test
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<div id='jsx-teardown'>
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```js
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console.info('after the test');
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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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