server.js

const express = require("express");
const mongoose = require("mongoose");
const bodyParser = require("body-parser");
const passport = require("passport");
const path=require("path")
const cors = require("cors")

const users = require("./routes/api/users");

const app = express();
app.use(cors())
// Bodyparser middleware
app.use(
  bodyParser.urlencoded({
    extended: false
  })
);
app.use(bodyParser.json());

// DB Config
const db = require("./config/keys").mongoURI;

// Connect to MongoDB
mongoose
  .connect(
    db,
    { useNewUrlParser: true , useUnifiedTopology: true}
  )
  .then(() => console.log("MongoDB successfully connected"))
  .catch(err => console.log(err));

// Passport middleware
app.use(passport.initialize());

// Passport config
require("./config/passport")(passport);

// Routes
app.use("/api/users", users);

if(process.env.NODE_ENV==='production'){
  app.use(express.static('client/build'))
  app.get('*',(req,res)=>{
    res.sendFile(path.resolve(__dirname,'client','build','index.html'))
  })
}
const port = process.env.PORT || 5000;

app.listen(port, () => console.log(`Server up and running on port ${port} !`));