Super simple example of a React component consuming a Drupal node exposed via the core REST functionality in Drupal 8.

DrupalNode.js

import React from 'react';

/**
 * Super simple example of a React component consuming a Drupal node exposed via the core REST functionality in Drupal 8.
 */

export default class DrupalNode extends React.Component {
    constructor(props) {
        super(props);
        this.state = {
            node: []
        }
    }

    componentDidMount() {
        // Go out and grab the node we want to load from the REST API.
        fetch('http://nostalgichugle.nick.mystack.co/node/' + this.props.nid + '?_format=hal_json')
            .then(Response => Response.json())
            .then(res => {
                console.log(res);
                this.setState({
                    node: res,
                });
            })
            .catch(error => {
                console.log(error)
            })
    }

    render() { 

        // Test to see if we have a node body.
        if(this.state.node.body) {            
            return(
                <p>{ this.state.node.body[0].value}</p>
            )
        }
        else {
            // If we haven't loaded it yet then render a loader.
            return(
                <p>Loading...</p>
             );
        }
    }
}