126 lines
3.7 KiB
Markdown
126 lines
3.7 KiB
Markdown
---
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id: 5a24c314108439a4d4036164
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title: Create a Component with Composition
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challengeType: 6
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isRequired: false
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forumTopicId: 301383
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---
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## Description
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<section id='description'>
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Now we will look at how we can compose multiple React components together. Imagine you are building an App and have created three components, a <code>Navbar</code>, <code>Dashboard</code>, and <code>Footer</code>.
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To compose these components together, you could create an <code>App</code> <i>parent</i> component which renders each of these three components as <i>children</i>. To render a component as a child in a React component, you include the component name written as a custom HTML tag in the JSX. For example, in the <code>render</code> method you could write:
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```jsx
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return (
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<App>
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<Navbar />
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<Dashboard />
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<Footer />
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</App>
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)
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```
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When React encounters a custom HTML tag that references another component (a component name wrapped in <code>< /></code> like in this example), it renders the markup for that component in the location of the tag. This should illustrate the parent/child relationship between the <code>App</code> component and the <code>Navbar</code>, <code>Dashboard</code>, and <code>Footer</code>.
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</section>
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## Instructions
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<section id='instructions'>
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In the code editor, there is a simple functional component called <code>ChildComponent</code> and a class component called <code>ParentComponent</code>. Compose the two together by rendering the <code>ChildComponent</code> within the <code>ParentComponent</code>. Make sure to close the <code>ChildComponent</code> tag with a forward slash.
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<strong>Note:</strong> <code>ChildComponent</code> is defined with an ES6 arrow function because this is a very common practice when using React. However, know that this is just a function. If you aren't familiar with the arrow function syntax, please refer to the JavaScript section.
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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 React component should return a single <code>div</code> element.
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testString: assert((function() { var shallowRender = Enzyme.shallow(React.createElement(ParentComponent)); return shallowRender.type() === 'div'; })());
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- text: The component should return two nested elements.
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testString: assert((function() { var shallowRender = Enzyme.shallow(React.createElement(ParentComponent)); return shallowRender.children().length === 2; })());
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- text: The component should return the ChildComponent as its second child.
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(ParentComponent)); return mockedComponent.find('ParentComponent').find('ChildComponent').length === 1; })());
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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 ChildComponent = () => {
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return (
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<div>
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<p>I am the child</p>
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</div>
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);
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};
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class ParentComponent 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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return (
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<div>
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<h1>I am the parent</h1>
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{ /* change code below this line */ }
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{ /* change code above this line */ }
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</div>
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);
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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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ReactDOM.render(<ParentComponent />, 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 ChildComponent = () => {
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return (
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<div>
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<p>I am the child</p>
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</div>
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);
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};
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class ParentComponent 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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return (
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<div>
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<h1>I am the parent</h1>
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{ /* change code below this line */ }
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<ChildComponent />
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{ /* change code above this line */ }
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</div>
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);
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}
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};
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```
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</section>
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