The connection string with the username password server and database is down below:

//imports
const express = require('express');
const mssql = require('mssql');
const body_parser = require('body-parser');
const app = express();

app.use(body_parser.json())

//connection string 
const dbConfig = {
    authentication: "Windows Authentication",
    username: "LAPTOP-JTDH0LQ5\Harsh",
    server: "LAPTOP-JTDH0LQ5\SQLEXPRESS",
    database: "crud_form",
    port: 1433
};

mssql.connect(dbConfig , err => {
    if (err){
        console.log("Error " + err.message);
    }
    else{
        console.log("Successful Connection!");
    }
})

When I run the code it says Server running on PORT 3000 for the first 15 seconds after which it crashes and says:

Failed to connect ‘LAPTOP-JTDH0LQ5SQLEXPRESS in 15000ms’

although the verification details are alright
The TC/IP is enabled.

I checked the connection string again and verified the details with the SQL Server running.
I’ve restarted the SQL Server and the NodeJS server as well.
The problem still persists.