Class definition in React

#react #help

Does a Class component in React need to have a constructor like the following example:

class App extends React.Component {
    constructor() {
        super()
        this.state = {
            count: 0
        }
    }
render() {
  ...
}
}

Or now we can define a Class component without using a constructor, like the following example?:

class App extends React.Component {
        this.state = {
            count: 0
        }
render() {
  ...
}
}

Which one is correct?
Do we still need to write the constructor for a Class component?

Top comments (3)

Elango Sundar • Jan 19 '19

@kayut If you don't have child class means, you can use as second option like without constructor.

Krisztian Kecskes • Jan 19 '19

dev.to/kozakrisz/react---es6-trick...

Sung M. Kim • Jan 20 '19

👆 answers the question 👍

@kayut
And note that the state is initialized as a property outside of constructor, this. should be dropped.

class App extends React.Component {
  // not this.state but just state
  state = {
    count: 0
  };
  render() { ...  }
}

DEV Community

Class definition in React

Top comments (3)

Read next

React 19 — New Features ️‍🔥

React + AWS Cognito: Email Authentication Setup Guide (First Part)

Simulating Mobile Virtual Keyboards in Progressive Web Apps

React v19 is out!