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>
79 lines
1.9 KiB
Markdown
79 lines
1.9 KiB
Markdown
---
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id: 5a24c314108439a4d403616b
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title: 使用默认的 Props
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challengeType: 6
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forumTopicId: 301418
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dashedName: use-default-props
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---
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# --description--
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React 还有一个设置默认 props 的选项。你可以将默认 props 作为组件本身的属性分配给组件，React 会在必要时分配默认 prop。如果没有显式的提供任何值，这允许你指定 prop 值应该是什么。例如，如果你声明`MyComponent.defaultProps = { location: 'San Francisco' }`，即定义一个 location 属性，并且其值在没有另行制定的情况下被设置为字符串`San Francisco`。如果 props 未定义，则 React 会分配默认 props，但如果你将`null`作为 prop 的值，它将保持`null`。
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# --instructions--
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代码编辑器中有一个`ShoppingCart`组件。在这个组件上定义默认 props，它指定一个`items`prop，其值为`0`。
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# --hints--
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应该渲染`ShoppingCart`组件。
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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(ShoppingCart));
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return mockedComponent.find('ShoppingCart').length === 1;
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})()
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);
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```
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`ShoppingCart`组件应该有一个`{ items: 0 }`的默认 prop。
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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(ShoppingCart));
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mockedComponent.setProps({ items: undefined });
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return mockedComponent.find('ShoppingCart').props().items === 0;
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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(<ShoppingCart />, document.getElementById('root'))
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```
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## --seed-contents--
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```jsx
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const ShoppingCart = (props) => {
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return (
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<div>
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<h1>Shopping Cart Component</h1>
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</div>
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)
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};
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// Change code below this line
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```
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# --solutions--
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```jsx
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const ShoppingCart = (props) => {
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return (
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<div>
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<h1>Shopping Cart Component</h1>
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</div>
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)
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};
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// Change code below this line
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ShoppingCart.defaultProps = {
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items: 0
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}
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```
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