Function Inside Object in JavaScript

In JavaScript, functions can be defined inside objects, just like any other property. These functions are called "methods" and can be invoked by using the object's name, followed by the method name and parentheses.

For example:

const object = {
    method: function() {
console.log("Hello, I'm a method!");
    }
};

object.method(); // prints "Hello, I'm a method!"

You can also define methods using the shorthand notation, which uses the function keyword.

const object = {
method() {
console.log("Hello, I'm a method!");
    }
};

object.method(); // prints "Hello, I'm a method!"

You can also define methods using the arrow function notation, which is similar to the shorthand notation but uses the => instead of function keyword

const object = {
    method: () => {
console.log("Hello, I'm a method!");
    }
};

object.method(); // prints "Hello, I'm a method!"

Inside the method, you can access the properties of the object using the this keyword.

const object = {
    property: "I'm a property",
    method: function() {
        console.log(this.property);
    }
};

object.method(); // prints "I'm a property"

Methods can also accept parameters and return values just like regular functions:

const object = {
    method: function(a, b) {
        return a + b;
    }
};

console.log(object.method(1, 2)); // prints 3

You can also add methods to an object after it has been created by assigning a new method to an existing property, or by creating a new property on the object and assigning a method to it.

In javascript you can use class keyword to create objects with methods and properties, it follows the OOP concepts.

class Object {
constructor(){
this.property = "I'm a property";
    }
method(){
console.log("Hello, I'm a method!");
    }
}
const obj = new Object();
console.log(obj.property);
obj.method();

Overall, methods are an essential part of object-oriented programming in JavaScript and are a powerful tool for working with complex data structures.

function checkEligiblity(){
    if(this.age>=18){
        console.log(`${this.firstname} age is ${this.age} eligible for vote`);
    }else{
        console.log(`${this.firstname} age is ${this.age} not eligible for vote`);
    }
}

const user1={
    firstname:"Joes",
    age:35,
    eligiblity:checkEligiblity
}
user1.eligiblity();
const user2={
    firstname:"Sara",
    age:12,
    eligiblity:checkEligiblity
}
user2.eligiblity();

In JavaScript, it is common to define functions separately and then assign them to object properties as methods. In the above example, the function checkEligibility is defined separately and then assigned to the eligibility property of the user1 and user2 objects. This allows the function to be reused as a method for multiple objects.

When the method is invoked on the user1 object, this inside the method will refer to user1 object and when it is invoked on the user2 object, this inside the method will refer to user2 object, This way checkEligibility function can use the properties of the current object on which it is invoked.

In the example, user1.eligibility() is invoked, and it will execute the checkEligibility function. Inside the function, it uses the this keyword to access the properties of the user1 object, namely firstname and age. The function then checks if the person's age is greater than or equal to 18, and if so, logs a message saying that the person is eligible to vote.

Similarly, when user2.eligibility() is invoked, it will execute the checkEligibility function. Inside the function, it uses the this keyword to access the properties of the user2 object, namely firstname and age. The function then checks if the person's age is greater than or equal to 18, and if not, logs a message saying that the person is not eligible to vote.

In this way, the function checkEligibility is used as a method for different objects and it uses the this keyword to access the properties of the object that invokes it, making the function more reusable.

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