State in Class Based Components

In React, a state is an object that belongs to component which represents the current data of a component. In class-based components, state is defined using the constructor method, and can be accessed using the this.state syntax.

The state object contains data that can change over time, and whenever the state updates, React automatically re-renders the component to reflect the updated data. State is often used to represent user input, application data, and other dynamic values that need to be updated in response to user actions or other events.

For example, consider a simple component that displays a counter that can be incremented or decremented by the user:

import React, { Component } from 'react';

class Counter extends Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0
    };
  }

  increment() {
    this.setState({ count: this.state.count + 1 });
  }

  decrement() {
    this.setState({ count: this.state.count - 1 });
  }

  render() {
    return (
      <div>
        <p>Count: {this.state.count}</p>
        <button onClick={() => this.increment()}>Increment</button>
        <button onClick={() => this.decrement()}>Decrement</button>
      </div>
    );
  }
}

In this example, the component's state includes a count property that is initially set to 0. The increment and decrement methods update the count property using the setState method, which triggers a re-render of the component with the updated value. The render method displays the current count value and two buttons that allow the user to increment or decrement the count.

Why Super?

When defining the state of a class-based component in React, it is not strictly necessary to call the super() method in the constructor if you are not doing any additional initialization in the constructor.

If you do not need to do anything in the constructor besides setting the initial state, you can define the state object as a class property directly, like this:

class MyComponent extends React.Component {
  state = {
    count: 0
  };

  // ...
}

In this case, since the state is being defined as a class property instead of inside the constructor, there is no need to call super() because the constructor of the parent class is not being overridden.

If you do need to perform any additional initialization in the constructor before setting the state, you should call super(props) as the first line of the constructor to properly initialize the component, like this:

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    // perform any additional initialization here
    this.state = {
      count: 0
    };
  }

  // ...
}

In summary, whether or not to call super() in the constructor depends on whether you are doing any additional initialization besides setting the initial state. If not, you can define the state as a class property directly without calling super(). If you do need to perform any additional initialization, you should call super(props) as the first line of the constructor.