Use of super in React Class constructor

super.js

// ES6 class constructors MUST call super if they are subclasses. 
// Thus, you have to call super() if you have a constructor. 
// A subclass does not have to have a constructor (see #1) 

// #1 no need to call super() here as there is no constructor
class MyClass extends React.Component {
    render(){
        return <div>Hello { this.props.world }</div>;
    }
}

// #2 the effects of passing props into your Component
class MyClass extends React.Component{
    constructor(props){
        super();
        console.log(this.props); // this.props is undefined
    }
}

// #3 you also need to pass props to super()
class MyClass extends React.Component{
    constructor(props){
        super(props);
        console.log(this.props); // prints out whatever is inside props

    }
}

// #4 there is also no need to pass props into the constructor
class MyClass extends React.Component{
    render(){
        // There is no need to call `super(props)` or have a constructor 
        // this.props is automatically set for you by React 
        console.log(this.props);  // it works!

    }
}