What is ‘this’ in JavaScript?

Hello everyone, today's I am going to share a basic and very confusing concepts that is called 'this' keyword :)

The 'this' keyword behaves a little differently in JavaScript compared to other languages.

In most of the other languages, 'this' keyword is a reference to the current object instantiated by the classes and methods. 

In the JavaScript languages, 'this' keyword refers to the object which 'owns' the method, but it depends on how a function is called.

The examples in details as given below.

//Global Scope in JavaScript
//In the below example, ‘this’ keyword refers to the global object.

window.sms = "Hi, I am window object";

console.log(window.sms);
console.log(this.sms); // Hi, I am window object.
console.log(window === this); // Its return true.

//Calling a Function in JavaScript 
//In the below example, ‘this’ keyword remains the global object if we are calling a function.

window.sms = "Hi, I am window object";

// Creating a function
function thisMethod() {
    console.log(this.sms); // Hi, I am window object.
    console.log(window === this); //Its return true.
}

// Calling a function
thisMethod();

//Calling Object Methods in JavaScript
//In the below example, when we calling an object constructor or any of its methods, 
//‘this’ keyword refers to the instance of the object.

window.sms = "Hi, I am window object";

function objectTestMethod() {
    this.sms = "Hi, I am a test object.";
    this.method1 = function () {
        console.log(this.sms); // Hi, I am a test object.
    };
}

objectTestMethod.prototype. method2 = function () {
    console.log(this.sms); // Hi, I am a test object.
};

// Creating object and calling methods

var v = new objectTestMethod();
v. method1();
v. method2();