🛡️ Abstraction in JavaScript (OOP)

Last Updated: 24th October 2025

Abstraction means hiding the internal details of a class and showing only the necessary functionalities to the user.

Hinglish Tip 🗣: Jaise car chalana hai, aapko engine ka pura kaam samajhne ki zarurat nahi. Sirf start(), accelerate(), brake() methods use karte ho. Yehi hai abstraction.

📌 How to Achieve Abstraction in JS

  1. Using Classes and Methods
  2. Using private properties (#)
  3. Exposing only necessary methods

1. Example: Hiding Internal Data

class BankAccount {
  #balance; // private property

  constructor(initialBalance) {
    this.#balance = initialBalance;
  }

  deposit(amount) {
    this.#balance += amount;
    console.log(`Deposited ${amount}. Current Balance: ${this.#balance}`);
  }

  withdraw(amount) {
    if (amount <= this.#balance) {
      this.#balance -= amount;
      console.log(`Withdrew ${amount}. Current Balance: ${this.#balance}`);
    } else {
      console.log("Insufficient balance!");
    }
  }

  getBalance() {
    console.log(`Balance is ${this.#balance}`);
  }
}

const acc = new BankAccount(1000);
acc.deposit(500); // Deposited 500. Current Balance: 1500
acc.withdraw(200); // Withdrew 200. Current Balance: 1300
acc.getBalance(); // Balance is 1300

// Trying to access private property
console.log(acc.#balance); // SyntaxError

Hinglish Tip 🗣: #balance ko directly access nahi kar sakte → hidden from user. Only deposit, withdraw, getBalance are accessible → abstraction.

2. Abstract Classes (Simulated)

JS doesn’t have true abstract classes, but we can throw error in base class to simulate.

class Vehicle {
  start() {
    throw new Error("Method 'start()' must be implemented.");
  }
}

class Car extends Vehicle {
  start() {
    console.log("Car started!");
  }
}

const myCar = new Car();
myCar.start(); // Car started!

const v = new Vehicle();
v.start(); // Error: Method 'start()' must be implemented.

Hinglish Tip 🗣: Base class ka method define karte hain but force karte hain child class implement kare → abstraction simulation.

💡 Quick Practice

  • Create Employee class with private property salary.
  • Add public methods setSalary(), getSalary().
  • Create Manager class extending Employee and test abstraction.
  • Exercise
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