Not able to connect express with mongodb while designing API

See more:

API

MongoDB

CORS

```

var express = require("express");
var cors = require("cors");
var mongoClient = require("mongodb").MongoClient;

var connectionString = "mongodb://127.0.0.1:27017";

var app = express();
app.use(cors());
app.use(express.urlencoded({
  extended:true
}));
app.use(express.json());

app.get("/getusers", (req, res)=>{
  mongoClient.connect(connectionString, (err, clientObj)=>{
    if (!err) {
      var database = clientObj.db("reactdb");
      database.collection("tblusers").find({}).toArray((err, documents) => {
          if (!err) {
            res.send(documents);
          }
        })
    }
  })
});

app.post("/registeruser", (req, res)=>{
  var userdetails = {
    UserId: req.body.UserId,
    UserName: req.body.UserName,
    Password: req.body.Password,
    Age: parseInt(req.body.Age),
    Mobile: req.body.Mobile,
    Subscribed: (req.body.Subscribed === "true")?true:false
  };
  mongoClient.connect(connectionString,(err, clientObj)=>{
    if(!err){
      var database = clientObj.db("reactdb");
      database.collection("tblusers").insertOne(userdetails,(err, result)=>{
        if(!err){
          console.log("Record Inserted...");
          res.redirect("/getusers");
        }
      })
    }
  })
})

app.listen(4000);
console.log("Server Started : http://127.0.0.1:4000");

```

What I have tried:

I was trying to build a simple MERN stack application and while building that I wanted to create my own API, so I created a server folder and made a file with the name api.js inside it. Which is given above and tried to connect it with my mongodb database but when I type http://127.0.0.1:4000/getusers and hit enter it keeps loading and doesn't show anything. I tried to use postman also, but nothing happened, it keeps loading.