Firebase NodeJs ReferenceError: Promise is not defined - node.js

Question

I came across this error message when trying to deploy a firebase node application to a virtual private server:
/home/.../Backend/node_modules/firebase-admin/lib/firebase-namespace.js:195
this.Promise = Promise;
^
ReferenceError: Promise is not defined
at new FirebaseNamespace (/home/.../Backend/node_modules/firebase-admin/lib/firebase-namespace.js:195:24)
at Object.<anonymous> (/home/.../Backend/node_modules/firebase-admin/lib/default-namespace.js:5:21)
at Module._compile (module.js:456:26)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.require (module.js:364:17)
at require (module.js:380:17)
at Object.<anonymous> (/home/.../Backend/node_modules/firebase-admin/lib/index.js:4:16)
at Module._compile (module.js:456:26)
On my local environment, this node application runs without any problem. Both environments are having the same node, npm, and "firebase-admin" module version.
So, I followed the suggestion from here and modified the "firebase-admin" module files on the virtual server. By adding
var Promise = require('es6-promise').Promise;
to some of the module source files manually, I can get rid of the error messages. After that, nothing can be read from the firebase database.
My code section
firebaseDatabase.ref("...").once('value').then(function(snapshot){
....
});
which reads the contents of firebase with no problem on my local environment, never have its "then" called on the virtual server.
What am I doing wrong? Any suggestion is appreciated.

Answer 1

I manage to solved the problem. Just in case if anyone run into the same issue, here are the steps how I fixed it:
For my case, I removed all the modifications I made to the firebase-admin module.
install "es6-promise" if you haven't. (npm install es6-promise --save)
Add the following line to your "server.js" file:
require('es6-promise').polyfill();
Notice that we don't assign the result of polyfill() to any variable. The polyfill() method will patch the global environment (in this case to the Promise name) when called.

Answer 2

I encountered this issue as soon as I firebase init. I did not change or added any codes in the generated scripts. I did solve the issue and was able to deploy by:
Going to the functions folder "cd functions"
sudo npm install es6-promise --save
Browse to the functions/node_modules/firebase-admin/lib/firebase-namespace.js
Add this on top
var Promise = require('es6-promise').Promise;
Your header should look like this:
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var deep_copy_1 = require("./utils/deep-copy");
var error_1 = require("./utils/error");
var firebase_app_1 = require("./firebase-app");
var credential_1 = require("./auth/credential");
var DEFAULT_APP_NAME = '[DEFAULT]';
var globalAppDefaultCred;
var globalCertCreds = {};
var globalRefreshTokenCreds = {};
var Promise = require('es6-promise').Promise;