server.js

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

var app = express();
app.use(bodyParser.json()); //need to parse HTTP request body

var config = {
	databaseURL: "",
	type: "",
	project_id: "",
	private_key_id: "",
	private_key: "",
	client_email: "",
	auth_uri: "",
	token_uri: "",
	auth_provider_x509_cert_url: "",
	client_x509_cert_url: ""
}
  
firebase.initializeApp(config);
  
//Fetch instances
app.get('/', function (req, res) {

	console.log("HTTP Get Request");
	var userReference = firebase.database().ref("/users/");

	//Attach an asynchronous callback to read the data
	userReference.once("value", 
			  function(snapshot) {
					console.log(snapshot.val());
					res.json(snapshot.val());
					userReference.off("value");
					}, 
			  function (errorObject) {
					console.log("The read failed: " + errorObject.code);
					res.send("The read failed: " + errorObject.code);
			 });
});

//Create new instance
app.put('/', function (req, res) {

	console.log("HTTP Put Request");

	var userName = req.body.UserName;
	var name = req.body.Name;
	var age = req.body.Age;
	console.log(req.body);
	
	var referencePath = '/users/data/0/';
	var userReference = firebase.database().ref(referencePath);
	userReference.set({Name: name, Age: age}, 
				 function(error) {
					if (error) {
						res.send("Data could not be saved." + error);
					} 
					else {
						res.send("Data saved successfully.");
					}
			});
});

//Update existing instance
app.post('/', function (req, res) {

	console.log("HTTP POST Request");

	var userName = req.body.UserName;
	var name = req.body.Name;
	var age = req.body.Age;

	var referencePath = '/Users/'+userName+'/';
	var userReference = firebase.database().ref(referencePath);
	userReference.update({Name: name, Age: age}, 
				 function(error) {
					if (error) {
						res.send("Data could not be updated." + error);
					} 
					else {
						res.send("Data updated successfully.");
					}
			    });
});

//Delete an instance
app.delete('/', function (req, res) {

   console.log("HTTP DELETE Request");
   var userName = req.body.UserName;
	var name = req.body.Name;
	var age = req.body.Age;

	var referencePath = '/Users/'+userName+'/';
	var userReference = firebase.database().ref(referencePath);
    userReference.remove()
    .then(function() {
        console.log("Remove succeeded.")
      })
      .catch(function(error) {
        console.log("Remove failed: " + error.message)
      });
   
});

var server = app.listen(8080, function () {
  
   var host = server.address().address;
   var port = server.address().port;
   
   console.log("Example app listening at http://%s:%s", host, port);
});