What does calling super() in a React constructor do?

Question

Learning React from the docs and came across this example:

class Square extends React.Component {
  constructor() {
    super();
    this.state = {
      value: null,
    };
  }
  ...
}

According to Mozilla, super allows you to use this in the constructor. Is there any other reason to use a stand alone super (I know super allows you to access parent class's methods as well) but with React is there any other use case of just calling super() by itself?

Answer 1

super() will calls the constructor of its parent class. This is required when you need to access some variables from the parent class.

In React, when you call super with props. React will make props available across the component through this.props. See example 2 below

without super()

class A {
  constructor() {
    this.a = 'hello'
  }
}

class B extends A {
  constructor(){
    console.log(this.a) //throws an error
  }
}

console.log(new B())

with super()

class A {
  constructor(props) {
    this.props = props
  }
}

class B extends A {
  constructor(props) {
    super(props)
    console.log(this.props)
  }
}

console.log(new B({title: 'hello world'}))

Hope this helps!