83 lines
2.4 KiB
Markdown
83 lines
2.4 KiB
Markdown
---
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id: 5a24c314108439a4d403616b
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title: Use Default Props
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challengeType: 6
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isRequired: false
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---
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## Description
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<section id='description'>
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React also has an option to set default props. You can assign default props to a component as a property on the component itself and React assigns the default prop if necessary. This allows you to specify what a prop value should be if no value is explicitly provided. For example, if you declare <code>MyComponent.defaultProps = { location: 'San Francisco' }</code>, you have defined a location prop that's set to the string <code>San Francisco</code>, unless you specify otherwise. React assigns default props if props are undefined, but if you pass <code>null</code> as the value for a prop, it will remain <code>null</code>.
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</section>
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## Instructions
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<section id='instructions'>
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The code editor shows a <code>ShoppingCart</code> component. Define default props on this component which specify a prop <code>items</code> with a value of <code>0</code>.
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</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: The <code>ShoppingCart</code> component should render.
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(ShoppingCart)); return mockedComponent.find('ShoppingCart').length === 1; })(), 'The <code>ShoppingCart</code> component should render.');
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- text: 'The <code>ShoppingCart</code> component should have a default prop of <code>{ items: 0 }</code>.'
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testString: 'assert((function() { const mockedComponent = Enzyme.mount(React.createElement(ShoppingCart)); mockedComponent.setProps({items: undefined}); return mockedComponent.find(''ShoppingCart'').props().items === 0; })(), ''The <code>ShoppingCart</code> component should have a default prop of <code>{ items: 0 }</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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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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</div>
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### After Test
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<div id='jsx-teardown'>
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```js
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ReactDOM.render(<ShoppingCart />, document.getElementById('root'))
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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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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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</section>
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