Connecting APIs node.js backend (firebase) with react.js

Question

I am having trouble connecting my node.js back-end code that is connected and working fine when they run on back-end, but when I try to use these functions in the front-end react.js it doesn't work. I am receiving an error of unexpected token, I think because it is fetching the wrong data.

Here's my back-end desktop\test\src\users.js:

var express  = require('express');

var app   = express();                             

var Firebase = require('firebase');

var morgan = require('morgan');      

var bodyParser = require('body-parser');    

var Rebase = require('re-base');

app.use(function(req, res, next) { 

res.setHeader("Access-Control-Allow-Origin", "*");

res.header("Access-Control-Allow-Methods", "POST, PUT, OPTIONS, DELETE, GET");

res.header("Access-Control-Max-Age", "3600");

res.header("Access-Control-Allow-Headers", "Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With");

next();

});


Firebase.initializeApp({

apiKey: test.apiKey,

authDomain: test.authDomain,

databaseURL: test.databaseURL,

projectId: test.projectId,

storageBucket: test.storageBucket,

messagingSenderId: test.messagingSenderId,

serviceAccount: './testapp.json', 

});


var db = Firebase.database();

var usersRef = db.ref("Users/");
console.log("reached here.");
 app.get('/api/users', function(req, res) 
 {
     var array = [];
     usersRef.on("value", function(snapshot)
     {
         snapshot.forEach(function(data) 
         {
             var usernames =data.child("username").val();
             var user = { "username": usernames};
             array.push(user);
         });
          res.json(array);
      });
     });
     app.listen(8000);

 console.log("port is 8000");

desktop\test\src\test.js contains my firebase information. I've put X's just for the sake of showing it here.

module.exports = {     
apiKey: "XXXXXXXXXXXXXXXXXXXXXXUrQT8_WyGeZYSkNIA",
authDomain: "authentication-efba4.firebaseapp.com",
databaseURL: "https://authentication-efba4.firebaseio.com",
projectId: "authentication-efba4",
storageBucket: "authentication-efba4.appspot.com",
messagingSenderId: "XXXXX8179075"

 };

Here's my front-end desktop\test\src\App.js:

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

class App extends Component {
  state = {users: []}

  componentDidMount() {
    fetch('/users')
      .then(res => res.json())
      .then(users => this.setState({ users }));
  }

  render() {
    return (
      <div className="App">
        <h1>Users</h1>
        {this.state.users.map(user =>
          <div key={user.id}>{user.username}</div>
        )}
     </div>
    );
  }
}

export default App;

It is not fetching the data from the database, I cannot even compile it when I run yarn start. I get this error:

Unhandled Rejection (SyntaxError): Unexpected token < in JSON at position 0
 6 | 
 7 | componentDidMount() {
 8 |   fetch('/users')
 9 |     .then(res => res.json()) <--
10 |     .then(users => this.setState({ users }));
11 | }
12 |

Are your react app and your node app running on the same port? If not you will have to run them on the same port or through a reverse proxy — A. Llorente
– A. Llorente, Commented Jun 19, 2018 at 6:01
Yes I even tried to use 3001 in my users.js and added a proxy in my package.json to be 3001. Also, here's how my firebase database looks like: link — Rayes
– Rayes, Commented Jun 19, 2018 at 6:07

Rahul · Accepted Answer · 2018-06-19 06:10:22Z

1

Take a snapshot of database using below function

var ref = db.ref("server/saving-data/fireblog/posts");

// Attach an asynchronous callback to read the data at our posts reference
ref.on("value", function(snapshot) {
  console.log(snapshot.val());
}, function (errorObject) {
  console.log("The read failed: " + errorObject.code);
});

Ref : https://firebase.google.com/docs/database/admin/retrieve-data

answered Jun 19, 2018 at 6:10

Rahul

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