Why am I getting 'Application Error' when deploying to Heroku? (MERN app) - heroku

Question

I've checked the logs and this is what it says:
Here is my app.js file (at the root level):
// Importing frameworks, libraries, routes, and JSON parser
const express = require('express');
const mongoose = require('mongoose');
const rewards = require('./routes/api/rewards');
const bodyParser = require('body-parser');
const path = require('path');
// Loading static build folder for production
if (process.env.NODE_ENV === 'production') {
app.use(express.static('frontend/build'));
app.get('/', (req, res) => {
res.sendFile(path.resolve(__dirname, 'frontend', 'build', 'index.html'));
})
}
// Create a new Express server
const app = express();
// Setup middleware for body parser
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());
// Import MongoDB key
const db = require('./config/keys').mongoURI;
// Connect to MongoDB using Mongoose
mongoose
.connect(db, {useNewUrlParser: true, useUnifiedTopology: true})
.then(() => console.log('Connected to MongoDB successfully'))
.catch(err => console.log(err));
// Create basic express routing
app.use('/api/rewards', rewards);
// Determining which port to run on
// Deploying on Heroku requires the server to be on process.env.PORT
const port = process.env.PORT || 5000;
// Start a socket and listen for connections on the path
// Display a success message when server is running correctly
app.listen(port, () => console.log(`Server is running on port ${port}`));
Any pointers/tips on what this error message is saying exactly? My best guess is that it has something to with one of my routes but I'm not too sure...

Answer 1

You are making your app variable below your if of production check to serve react build.
please move line
const app = express();
above your if check.
correct app.js would be:
// Importing frameworks, libraries, routes, and JSON parser
const express = require('express');
const mongoose = require('mongoose');
const rewards = require('./routes/api/rewards');
const bodyParser = require('body-parser');
const path = require('path');
// Create a new Express server
const app = express();
// Loading static build folder for production
if (process.env.NODE_ENV === 'production') {
app.use(express.static('frontend/build'));
app.get('/', (req, res) => {
res.sendFile(path.resolve(__dirname, 'frontend', 'build', 'index.html'));
})
}
// Setup middleware for body parser
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());
// Import MongoDB key
const db = require('./config/keys').mongoURI;
// Connect to MongoDB using Mongoose
mongoose
.connect(db, {useNewUrlParser: true, useUnifiedTopology: true})
.then(() => console.log('Connected to MongoDB successfully'))
.catch(err => console.log(err));
// Create basic express routing
app.use('/api/rewards', rewards);
// Determining which port to run on
// Deploying on Heroku requires the server to be on process.env.PORT
const port = process.env.PORT || 5000;
// Start a socket and listen for connections on the path
// Display a success message when server is running correctly
app.listen(port, () => console.log(`Server is running on port ${port}`));