react.md

React

2. Write a react component "PrintHeadline" that renders a variable H1 headline using attribute "myHeadline" !

   // Example usage: <PrintHeadline myHeadline="this is a variable Headline" />
   
   // Class Component
   class PrintHeadline extends React.Component {
       render() {
           return <h1>{this.props.myHeadline}</h1>
       }
   }
   
   // Functional Component
   function PrintHeadline(props) {
       return <h1>{props.myHeadline}</h1>;
   }

3. Which method must be implemented by a react component at least that returns HTML code?

   // Class Component: render()
   render(){
       return(<h1>Hallo</h1>)
   }
   
   //Functional Component
   return(<h1>Hallo</h1>)

4. Which data structure should be used to access input data that is passed into a react component?

   // Class Component: object
   this.props

5. When a react component’s state data changes, which method will be invoked to update the rendered markup?

   // Class Component
   render()

6. Which data structure holds the state data in a react component?

   // Class Component: object
   this.state

7. Which react method must be called to set a state property?

   // Class Component: setState({key: value})
   this.setState((state) => {
       return {counter: state.counter + 1}
   })
   
   // Functional Component
   const [someState, setSomeState] = useState();
   setSomeState("muss zur Änderung aufgerufen werden");

8. Which react method must be called in a components constructor to properly handle passed input data?

   // Class Component
   super(props)