Assalamualaikum, hello guys in this article we will connect a database with javascript, than create a simple crud system with javascript.

1. Install Package on NPM

First, we need some a package:

pg
readline/promise (default available in node.js)

npm i pg
npm i readline/promise (optional)

2. Create DataBase on Postgres

Second, we need database to save data from query

create database school;

create table students (
id serial primary key,
name varchar(100) not null,
address varchar(150) not null
);

3. Create a File & CRUD with the file

3.1 Create a File to Save Package Pg

Third, we will create a file name is db.js on folder utils, and add this code:

import pg from 'pg';

const pool = new pg.Pool({
  user: 'postgres',
  host: 'localhost',
  database: 'school',
  password: '<your_password>',
  port: 5432,
});

export default pool;

3.2 Create a File to Save Package Readline

Fourth, we will create a file name is rideline.js on folder utils, and add this code:

import readline from 'node:readline/promises';
import {stdin as input, stdout as output } from 'node:process';

const rl = readline.createInterface({input, output})

export async function inputData(question){
    const answer = await rl.question(`${question}`)
    return answer.trim()
}

export async function closeInput() {
    await rl.close();
}

3.3 Create System Create Data

Fifth, we will create a file to system create data for database name file is 1-create.js, add this code:

//file 1-create.js
import pool from './utils/db.js';
import {inputData, closeInput} from './utils/app.js'

export default async function addStudent() {
  try {
    const queryText = `
    INSERT INTO students(name, address) VALUES($1, $2) RETURNING *
    `;
    const res = await pool.query(
    queryText, 
    [studentName, studentAddress]
    );

    console.log('new student success add on database:');
    console.log(res.rows[0]); 
  } catch (err) {
    console.error('failed add student data:', err.stack);
  } finally {
    await pool.end();
    await closeInput();
  }
}

addStudent();

when you running in terminal, display this:

2.4 Create System Read Data

Sixth, we will create a file to system read data for database name file is 2-read.js, add this code:

//file 2-read.js
import pool from './utils/db.js';
export default async function seeStudent() {
  try {
    const res = await pool.query('
    SELECT * FROM student ORDER BY id ASC
    ');

    if (res.rows.length === 0) {
      console.log('not found student data.');
      return;
    }

    console.log('data student:');
    res.rows.forEach(santri => {
      console.log(
    `ID: ${santri.id}, 
    Name: ${student.name}, 
    address: ${student.address}`);
    });

  } catch (err) {
    console.error('failed ride data student:', err.stack);
  } 
}

seeStudent();

when we running this, display this:

3.5 Create System Update Data

Seventh, we will create a file to system update data for database name file is 3-update.js, add this code:

//file 3-update.js
import pool from './utils/db.js';
import {inputData, closeInput} from './utils/app.js'

export default async function updateStudent() {
  try {
    const res = await pool.query(
    'UPDATE students SET nama = $1, alamat = $2 WHERE id = $3', 
    [choice_name, choice_address, choice_id]
    );

    console.log('new student success add on database:');
    console.log(res.rows[choice_id]);
  } catch (err) {
    console.error('failed update data student:', err.stack);
  }
}

updateStudent();

when we running this, display this:

3.6 Create System Delete Data

Eighth, we will create a file to system update data for database name file is 4-delete.js, add this code:

//file 4-delete.js
import pool from './utils/db.js';
import {inputData, closeInput} from './utils/app.js'

export default async function deleteStudent() {
  try {

    const queryText = await pool.query('
    DELETE FROM students WHERE id = $1', [choice_id]
    );

    console.log('new student success add on database:');
  } catch (err) {
    console.error('failed delete data student:', err.stack);
  } 
}

deleteStudent();

when we running this, display this:

last, we will create a file to running all previes file

import { inputData, closeInput } from './utils/readline.js';
import pool from './utils/db.js';
import addStudent from './1-create.js';
import seeStudent from './2-read.js';
import updateStudent from './3-update.js';
import deleteStudent from './4-delete.js';

function showMenu() {
  console.log("\n=== DATEABASE SERVICES ===");
  console.log("1) Create Database");
  console.log("2) Read Database");
  console.log("3) Update Database");
  console.log("4) Delete Database");
  console.log("0) Close Shop");
}

async function askCreate() {
  const nameStudent = await inputData("student name?");
  const addressStudent = await inputData('student address?');
  await tambahSantri(nameStudent, addressStudent);
}


async function askUpdate() {
  const choice_id = await inputData("how much id update:");
  const choice_name = await inputData("new name?:")
  const choice_address = await inputData("new address?")
  await updateSantri(choice_id, choice_name, choice_address);
}

async function askDelete() {
  const choice_id = await inputData("how much id will delete:");
  await deleteSantri(choice_id);
}

async function serviceLoop() {
  while (true) {
    showMenu();
    const choice = await inputData("Choose a CRUD Database (number): ");

    switch (choice) {
      case "1":
        await askCreate();
        break;

      case "2":
        await seeStudent()
        break;

      case "3":
        await askUpdate()
        break;

      case "4":
        await askDelete()
        break

      case "0":
        console.log("\nShop closed. Thank you.\n");
        await pool.end()
        await closeInput()
        return;

      default:
        console.log("Invalid choice. Please try again.\n");
    }
  }
}

serviceLoop();