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Components and Props

Returning HTML Elements and Components

A function component can return any JSX, including a mix of HTML elements and custom React components.

In the example, we return a <Logo /> component and a “vanilla” HTML title.

This assumes that <Logo /> is defined elsewhere.

function Header() {
  return (
    <div>
      <Logo />
      <h1>Codecademy</h1>
    </div>
  );
}

Accessing Props

React components can access their props with the props object.

In the example code below, we see the <Hello> component being rendered with a firstName prop. It is accessed in the component’s return statement with props.firstName.

This should render the text “Hi there, Kim!”

function Hello(props) {
  return <h1>Hi there, {props.firstName}!</h1>;
}


ReactDOM.createRoot(document.getElementById('app')).render(<Hello firstName="Kim" />)

defaultProps

A React component can contain default values to be used in case props are not passed. If any prop is not passed to a Component, its value will be replaced by the prop of the same name.

In the example code, defaultProps is set so that profiles have a fallback profile picture if none is set. The <MyFriends> component should return two profiles: one with a set profile picture and one with the fallback profile picture.

function Profile(props) {
  return (
    <div>
      <img src={props.profilePictureSrc} alt="" />
      <h2>{props.name}</h2>
    </div>
  );
}


Profile.defaultProps = {
  profilePictureSrc: 'https://example.com/no-profile-picture.jpg',
};


function MyFriends(props) {
  return (
    <div>
      <h1>My friends</h1>
      <Profile
        name="Jane Doe"
        profilePictureSrc="https://example.com/jane-doe.jpg"
      />
      <Profile name="John Smith" />
    </div>
  );
}

props

Components can pass information to other components. When one component passes information to another, it is passed as props through one or more attributes.

The example code demonstrates the use of attributes in props. SpaceShip is the component and ride is the attribute. The SpaceShip component will receive ride in its props.

<SpaceShip ride="Millennium Falcon" />

props.children

Every component’s props object has a property named children. Using props.children will return everything in between a component’s opening and closing JSX tags.

<List>  // opening tag
  <li></li> // child 1
  <li></li> // child 2
  <li></li> // child 3
</List> // closing tag
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