React JSON.parse syntax error on response from express

Question

I have a simple node.js express server like so:

const express = require('express');
const app = express();
const port = process.env.PORT || 5000;

app.listen(port, () => console.log(`Listening on port ${port}`));

app.get('/express_backend', (req, res) => {
  res.send({ express: 'YOUR EXPRESS BACKEND IS CONNECTED TO REACT' });
});

and have the proxy set up in the package.json like so:

"proxy": "http://localhost:5000/"

With the following App.js file

class App extends Component {

  constructor(){
    super();
    this.state = {data: "asdf"};
  }

  componentDidMount() {
    fetch('/express_backend')
      .then(res => res.json())
      .then(res => this.setState({data: res.express}));
  }

I am running both node server.js and npm start at this time.

However, when I run it, I get the following message in the console for the line react-dom.development.js:26607 :

SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data

The contents of the response for "/express_backend" are:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <link rel="shortcut icon" href="/favicon.ico" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <meta name="theme-color" content="#000000" />
    <meta
      name="description"
      content="Web site created using create-react-app"
    />
    <link rel="apple-touch-icon" href="logo192.png" />
    <!--
      manifest.json provides metadata used when your web app is installed on a
      user's mobile device or desktop. See https://developers.google.com/web/fundamentals/web-app-manifest/
    -->
    <link rel="manifest" href="/manifest.json" />
    <!--
      Notice the use of  in the tags above.
      It will be replaced with the URL of the `public` folder during the build.
      Only files inside the `public` folder can be referenced from the HTML.

      Unlike "/favicon.ico" or "favicon.ico", "/favicon.ico" will
      work correctly both with client-side routing and a non-root public URL.
      Learn how to configure a non-root public URL by running `npm run build`.
    -->
    <title>React App</title>
  </head>
  <body>
    <noscript>You need to enable JavaScript to run this app.</noscript>
    <div id="root"></div>
    <!--
      This HTML file is a template.
      If you open it directly in the browser, you will see an empty page.

      You can add webfonts, meta tags, or analytics to this file.
      The build step will place the bundled scripts into the <body> tag.

      To begin the development, run `npm start` or `yarn start`.
      To create a production bundle, use `npm run build` or `yarn build`.
    -->
  <script src="/static/js/bundle.js"></script><script src="/static/js/0.chunk.js"></script><script src="/static/js/main.chunk.js"></script></body>
</html>

I'm now getting this as well, if it is of any use:

Source map error: SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data
Resource URL: http://localhost:3000/
Source Map URL: ../sourcemaps/inpage.js.map

Answer 1

You replaced res.send with res.json .
Instead of relying on res.json() to call JSON.stringify for you, try to do it explicitly:

res.json(JSON.stringify({ express: 'YOUR EXPRESS BACKEND IS CONNECTED TO REACT' }))

React JSON.parse syntax error on response from express

Question

1 answers

solution1
0 2019-09-13 02:11:14

React JSON.parse syntax error on response from express

Question

1 answers

solution1 0 2019-09-13 02:11:14

solution1
0 2019-09-13 02:11:14