App.js

import React, { Component } from 'react';
import './App.css';

class App extends Component {
  constructor(props) {
    super(props);
    this.state = {dataText: "data not yet recieved"};
  }

  // this is called once the component is rendered at least once
  componentDidMount() {
    fetch("/greet")
        .then(data => data.text())
        .then(text => this.updateRecievedText(text));
  }

  updateRecievedText(text) {
    if (text == "hi") {
      this.setState({dataText: "Talking to Express server"});
    } else {
      this.setState({dataText: "This isn't the Express server"});
    }
  }


  render() {
    return (
      <div className="App">
        Status: {this.state.dataText}
      </div>
    );
  }
}

export default App;