A child class constructor cannot make use of this reference until the super() method has been called. The same applies to ES6 sub-classes as well. The main reason for passing props parameter to super() call is to access this.props in your child constructors.
Passing props:
class MyComponent extends React.Component {
constructor(props) {
super(props);
console.log(this.props); // prints { name: 'John', age: 42 }
}
}Not passing props:
class MyComponent extends React.Component {
constructor(props) {
super();
console.log(this.props); // prints undefined
// but props parameter is still available
console.log(props); // prints { name: 'John', age: 42 }
}
render() {
// no difference outside constructor
console.log(this.props); // prints { name: 'John', age: 42 }
}
}The above code snippets reveals that this.props is different only within the constructor. It would be the same outside the constructor.
