80 lines
2.7 KiB
Markdown
80 lines
2.7 KiB
Markdown
---
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id: 5a24c314108439a4d403616c
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title: Override Default Props
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challengeType: 6
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isRequired: false
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videoUrl: ''
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localeTitle: 覆盖默认道具
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---
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## Description
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<section id="description">设置默认道具的能力是React中的一个有用功能。覆盖默认道具的方法是显式设置组件的prop值。 </section>
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## Instructions
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<section id="instructions"> <code>ShoppingCart</code>组件现在呈现子组件<code>Items</code> 。此<code>Items</code>组件的默认prop <code>quantity</code>设置为整数<code>0</code> 。通过为<code>quantity</code>传递值<code>10</code>来覆盖默认支柱。 <strong>注意：</strong>请记住，向组件添加prop的语法与添加HTML属性的方式类似。但是，由于<code>quantity</code>的值是一个整数，因此它不会引用引号，但应该用大括号括起来。例如， <code>{100}</code> 。此语法告诉JSX将大括号内的值直接解释为JavaScript。 </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>ShoppingCart</code>应该呈现组件。
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testString: 'assert((function() { const mockedComponent = Enzyme.mount(React.createElement(ShoppingCart)); return mockedComponent.find("ShoppingCart").length === 1; })(), "The component <code>ShoppingCart</code> should render.");'
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- text: 该组件<code>Items</code>应该呈现。
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testString: 'assert((function() { const mockedComponent = Enzyme.mount(React.createElement(ShoppingCart)); return mockedComponent.find("Items").length === 1; })(), "The component <code>Items</code> should render.");'
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- text: '<code>Items</code>组件应具有从<code>ShoppingCart</code>组件传递的<code>{ quantity: 10 }</code>的prop。'
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testString: 'getUserInput => assert((function() { const mockedComponent = Enzyme.mount(React.createElement(ShoppingCart)); return mockedComponent.find("Items").props().quantity == 10 && getUserInput("index").replace(/ /g,"").includes("<Itemsquantity={10}/>"); })(), "The <code>Items</code> component should have a prop of <code>{ quantity: 10 }</code> passed from the <code>ShoppingCart</code> component.");'
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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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const Items = (props) => {
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return <h1>Current Quantity of Items in Cart: {props.quantity}</h1>
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}
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Items.defaultProps = {
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quantity: 0
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}
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class ShoppingCart extends React.Component {
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constructor(props) {
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super(props);
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}
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render() {
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{ /* change code below this line */ }
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return <Items />
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{ /* change code above this line */ }
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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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