JavaScript Object Methods

Types of Object Methods

greet: function() {
    return "Hello!";
}

greet() {
    return "Hello!";
}

greet: () => {
    return "Hello!";
}

function sayHello() {
    return "Hello!";
}
obj.greet = sayHello;

🔹 Basic Object Methods

Here's how to define and use methods in objects:

let calculator = {
    x: 10,
    y: 5,
    
    // Method using function expression
    add: function() {
        return this.x + this.y;
    },
    
    // Method using ES6 shorthand
    subtract() {
        return this.x - this.y;
    },
    
    // Method with parameters
    multiply(a, b) {
        return a * b;
    }
};

console.log(calculator.add());        // 15
console.log(calculator.subtract());   // 5
console.log(calculator.multiply(3, 4)); // 12

🔹 Methods with 'this' Keyword

Use 'this' to access other properties within the same object:

let person = {
    firstName: "John",
    lastName: "Doe",
    age: 25,
    
    // Method that uses 'this'
    getFullName() {
        return this.firstName + " " + this.lastName;
    },
    
    // Method that modifies properties
    haveBirthday() {
        this.age++;
        return "Happy birthday! Now " + this.age + " years old.";
    },
    
    // Method with parameters
    introduce(greeting) {
        return greeting + ", I'm " + this.getFullName();
    }
};

console.log(person.getFullName());      // "John Doe"
console.log(person.haveBirthday());     // "Happy birthday! Now 26 years old."
console.log(person.introduce("Hi"));    // "Hi, I'm John Doe"

🔹 Adding Methods After Creation

You can add methods to existing objects:

let car = {
    brand: "Toyota",
    model: "Camry",
    year: 2022
};

// Add method using dot notation
car.getInfo = function() {
    return this.year + " " + this.brand + " " + this.model;
};

// Add method using bracket notation
car["start"] = function() {
    return "The " + this.brand + " is starting...";
};

console.log(car.getInfo());  // "2022 Toyota Camry"
console.log(car.start());    // "The Toyota is starting..."

🔹 Methods vs Functions

Understanding the difference between methods and regular functions:

// Regular function
function regularFunction() {
    return "I'm a regular function";
}

let myObject = {
    name: "Test Object",
    
    // Method - function inside an object
    myMethod() {
        return "I'm a method of " + this.name;
    },
    
    // Method calling another method
    callMyMethod() {
        return this.myMethod() + " - called from another method";
    }
};

console.log(regularFunction());           // "I'm a regular function"
console.log(myObject.myMethod());         // "I'm a method of Test Object"
console.log(myObject.callMyMethod());     // "I'm a method of Test Object - called from another method"

🔹 Real-World Example

A practical example of an object with multiple methods:

let bankAccount = {
    accountNumber: "12345",
    balance: 1000,
    
    // Method to check balance
    checkBalance() {
        return "Current balance: $" + this.balance;
    },
    
    // Method to deposit money
    deposit(amount) {
        if (amount > 0) {
            this.balance += amount;
            return "Deposited $" + amount + ". " + this.checkBalance();
        }
        return "Invalid deposit amount";
    },
    
    // Method to withdraw money
    withdraw(amount) {
        if (amount > 0 && amount <= this.balance) {
            this.balance -= amount;
            return "Withdrew $" + amount + ". " + this.checkBalance();
        }
        return "Invalid withdrawal amount or insufficient funds";
    }
};

console.log(bankAccount.checkBalance());    // "Current balance: $1000"
console.log(bankAccount.deposit(500));      // "Deposited $500. Current balance: $1500"
console.log(bankAccount.withdraw(200));     // "Withdrew $200. Current balance: $1300"