Creating a REST API Backend using Node.js, Express and Postgres

JavaScript Backend can be developed using Node.js, Express, and Postgres. This backend can do Query operations on the PostgreSQL database and provide the status or data on the REST API.

Installation Requirement:

  1. Node.js:

  2. PostgreSQL:

Testing for Successful Installation:



  1. Node.js:

    • Open Command Prompt or Terminal and type:

      node -v 

      The output must show some version number example:

      v12.14.0 

      Note: If it shows command not found then node.js is not installed successfully.

  2. Postgres:

    • Windows : Search for SQL Shell, if found the Installation is successful.
    • Linux or Mac: Type the command below:

       which psq 

      Note: If output present then it is installed successfully.

Steps to Setup Database:

  • Open the PostgresSQL Shell
  • Type the Database Credentials for local Setup or press enter in case you want to go with default values as shown below:
    Postgresql Database shell
  • Create the database using:

    create database gfgbackend;     
  • Switch to this database using:



    \c gfgbackend;
  • Create a test table using:

    create table test(id int not null); 
  • Insert values into test table using:

    insert into test values(1);  
    insert into test values(2);
  • Now try to validate whether the data is inserted into table using:

    select * from test;

    Insert and Select Statement

Steps to Create a Backend:

  • Go to the Directory where you want to create project
  • Initialize the Node Project using:

    npm init
  • Type the name of Project and Other Details or Press Enter if you want to go with Default
    npm init details
  • Install express using npm

    npm install --save express
  • Install the node-postgres Client using npm

    npm install --save pg
  • Install the postgres module for serializing and de-serializing JSON data in to hstore format using npm.

     npm install --save pg-hstore    
  • Create a file index.js as entry point to the backend.
  • Now Install body-parser using npm

    npm install --save body-parser
  • Now add the below code to index.js file which initiates the express server, creates a pool connection and also creates a REST API ‘/testdata’. Don’t forget to add your Password while pool creation in the below code.

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    // Entry Point of the API Server 
      
    const express = require('express');
      
    /* Creates an Express application. 
       The express() function is a top-level 
       function exported by the express module.
    */
    const app = express();
    const Pool = require('pg').Pool;
      
    const pool = new Pool({
        user: 'postgres',
        host: 'localhost',
        database: 'gfgbackend',
        password: 'postgres',
        dialect: 'postgres',
        port: 5432
    });
      
      
    /* To handle the HTTP Methods Body Parser 
       is used, Generally used to extract the 
       entire body portion of an incoming 
       request stream and exposes it on req.body 
    */
    const bodyParser = require('body-parser');
    app.use(bodyParser.json())
    app.use(bodyParser.urlencoded({ extended: false }));
      
      
    pool.connect((err, client, release) => {
        if (err) {
            return console.error(
                'Error acquiring client', err.stack)
        }
        client.query('SELECT NOW()', (err, result) => {
            release()
            if (err) {
                return console.error(
                    'Error executing query', err.stack)
            }
            console.log("Connected to Database !")
        })
    })
      
    app.get('/testdata', (req, res, next) => {
        console.log("TEST DATA :");
        pool.query('Select * from test')
            .then(testData => {
                console.log(testData);
                res.send(testData.rows);
            })
    })
      
    // Require the Routes API  
    // Create a Server and run it on the port 3000
    const server = app.listen(3000, function () {
        let host = server.address().address
        let port = server.address().port
        // Starting the Server at the port 3000
    })

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  • Now, start the backend server using:
    node index.js
  • Open Browser and try to router to:
    http://localhost:3000/testdata

    Now, you can see the data from test table as follows:
    REST API DATA

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