server.js

const express = require("express");
const mongoose = require("mongoose");
const bodyParser = require("body-parser");
const passport = require("passport");
const cors = require('cors');
const users = require("./routes/api/users");
const posts = require('./routes/api/posts')

const app = express();

// Bodyparser middleware
app.use(
  bodyParser.urlencoded({
    extended: false
  })
);
app.use(bodyParser.json());
app.use(cors());
app.use(function(req, res, next) {
  // Website you wish to allow to connect
res.header('Access-Control-Allow-Origin', '*');

// Request methods you wish to allow
res.header('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE');

// Request headers you wish to allow
res.header('Access-Control-Allow-Headers', 'X-Requested-With,content-type');

// Set to true if you need the website to include cookies in the requests sent
// to the API (e.g. in case you use sessions)
res.header('Access-Control-Allow-Credentials', true);

// Pass to next layer of middleware
next();
});
// DB Config
const db = require("./config/keys").mongoURI;

// Connect to MongoDB
mongoose
  .connect(
    db,
    { useNewUrlParser: 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);
app.use("/api/posts", posts)


const port = process.env.PORT || 5000;

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