79 lines
1.9 KiB
Markdown
79 lines
1.9 KiB
Markdown
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---
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id: 5a24c314108439a4d403616b
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title: Use Default 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 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 `MyComponent.defaultProps = { location: 'San Francisco' }`, you have defined a location prop that's set to the string `San Francisco`, unless you specify otherwise. React assigns default props if props are undefined, but if you pass `null` as the value for a prop, it will remain `null`.
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# --instructions--
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The code editor shows a `ShoppingCart` component. Define default props on this component which specify a prop `items` with a value of `0`.
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# --hints--
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The `ShoppingCart` component should render.
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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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The `ShoppingCart` component should have a default prop of `{ items: 0 }`.
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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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