What is the best practice to define props in React?

Question

What is the best practice to define props in a component class in React.js? And why?

Inside the class:

import React, { Component } from 'react';
import PropTypes from 'prop-types';

export default class MyComponent extends Component {
  static propTypes = {
    prop: PropTypes
  }

  render() {
    return (
      <div> </div>
    )
  }
};

or outside the class:

import React, { Component } from 'react';
import PropTypes from 'prop-types';

class MyComponent extends Component {
    render() {
        return (
            <div> </div>
        )
    }
};

MyComponent.propTypes = {
    prop: PropTypes
}

export default MyComponent;

Answer 1

Second option.

import React, { Component } from 'react';
import PropTypes from 'prop-types';

class MyComponent extends Component {
    render() {
        return (
            <div> </div>
        )
    }
};

MyComponent.propTypes = {
    prop: PropTypes
}

export default MyComponent;

Check Clean Code vs. Dirty Code: React Best Practices for reference.