react-component.js

// Class-based component state example
import React from 'react';

class MyComponent extends React.Component {
  constructor(props) {
    super(props);

    // Set the state
    this.state = {
      myValue = 'test'
    };
  }
  
  render() {
    // Show the value when rendering the component
    return <h1>{this.state.myValue}</h1>;
  } 
}