Express JS

Express JS is flexible NODE.JS web application framework that provides a robust set of features to develop mobile and web applications. 

It also facilitates the rapid development of Node based Web Applications.

Features of Express JS

• Allows setting up of middle-ware to respond to HTTP Requests.
• Defines a routing table which is used to perform different actions based on HTTP Method and URL

Pre-Requisites

1. Node JS

2. MS SQL Database (for demo - any database can be used)

Step-1

Step 1: Create a package.json file.

{
  "name": "<Application Name>",//e.g.  – node_app
  "version": "0.0.0",
  "description": "<Description about your application>",
  "main": "server.js",
    "dependencies": {
        "express": "4.14.0",
        "body-parser": "1.15.2",
         "mssql":"3.3.0"
    },
    "scripts": {
    "start": "node server.js"
  },
  "author": {
    "name": "<Your Name>",
    "email": "<Your Email>"
  }
}

Step-2

Step 2: Create server.js file.

//Initiallising node modules

var express = require("express");

var bodyParser = require("body-parser");

var sql = require("mssql");

var app = express();

// Setting Base directory

app.use(bodyParser.json());

//CORS Middleware

app.use(function (req, res, next) {

//Enabling CORS

res.header("Access-Control-Allow-Origin", "*");

res.header("Access-Control-Allow-Methods", "GET,HEAD,OPTIONS,POST,PUT");

res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, contentType,Content-Type, Accept, Authorization");

next();

});

//Setting up server

var server = app.listen(process.env.PORT || 8080, function () {

var port = server.address().port;

console.log("App now running on port", port);

});

//Initiallising connection string

var dbConfig = {

user: "<username>",

password: "<password>",

server: "<severName>",

    database: "<database",

    port: "<port>",

    requestTimeout: '10000',

    debug: true,

    dialect: "mssql",

    options: {

encrypt: true // Use this if you're on Windows Azure

}

};

var pool = function(){

var conn = new sql.Connection(dbConfig, function(err){

var request = new sql.Request(conn);

//console.dir(request);

return request;

});

return conn;

}

//Function to connect to database and execute query

var executeQuery = function(res, query){

    var dbConn = new sql.Connection(dbConfig);

    dbConn.connect().then(function () {

        var request = new sql.Request(dbConn);

        request.query(query).then(function (recordSet) {

            //console.log(recordSet);

            res.send(recordSet);

            dbConn.close();

        }).catch(function (err) {

            console.log(err);

            dbConn.close();

        });

    }).catch(function (err) {

        console.log(err);

    });

    

}

app.get("/api/dpc", function(req , res){

    var query = "select count(*) as count from [schema].[table]";

    executeQuery(res,query);

});

Step -3

npm install 

Step-4

node server.js

The node server will start running into port number 8080 with corresponding API Routes; you can point to the below URL to test the application.

http://localhost:8080.