Many Programmers feel comfortable to use Postgre SQL rather than MongoDB, member of MEAN Stack.

We are going to integrate Postgresql with NodeJS

To install NodeJS, please go through this Article

Now, when we are finished with Installation of NodeJS.

We are going to install Postgres

first, run a command

npm install pg --save

Sometimes it doesn't work, so use sudo

sudo npm install pg --save

after completing the installation, We will be using the below code in our file to execute query.
 

var pg = require('pg');
var conn = 'postgres://postgres:postgres@localhost:5432/first_app_developement';

var client = new pg.Client(conn);
client.connect();

Now, lets break each line to understand

var pg = require('pg');

In the above line, we include postgres module by require method and create an object named pg.

var conn = 'postgres://[username]:[password]@[host]:[port]/[database_name]'

Now, we are including postgres URL,

I have simplified, for your usability

var connectionString = 'postgres://postgres:postgres@localhost:5432/first_app_developement';

Next we have to create an object for our postgres client

var client = new pg.Client(conn);

In this we have created an object of Client with corresponding database.

At last we need to connect our Client

client.connect();

Viola, we are connected !!!.