PropTypes

React has built-in typechecking on the props of components. This typechecking helps developers catch bugs and broadcast to other developers exactly what data types components' props expect.

Consider the Welcome.js example from the components section with an added PropType:

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

class Welcome extends Component {
  render () {
    return (
      <div>
        <p>Hello, {this.props.name}!</p>
      </div>
    );
  }
}

Welcome.propTypes = {
  name: PropTypes.string.isRequired
}

export default Welcome;

Try passing a non-string to the name prop or not passing the name prop at all. Now check the console. Hooray for errors!

There are many PropTypes to consider. Refer to the React documentation when using PropTypes.