Today I Learned Object,This keyword,Hoisting..

Object in JavaScript:

An object in JavaScript is a way to store related data and functions together in a single container, using key-value pairs.

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Basic Example:

const car = {
  brand: "Toyota",
  model: "Corolla",
  year: 2020
};

• brand, model, and year are keys (also called properties).
• "Toyota", "Corolla", and 2020 are values.

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Accessing Values:

console.log(car.brand);   // Output: "Toyota"
console.log(car["year"]); // Output: 2020

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Adding or Changing Properties:

car.color = "red";         // add a new property
car.year = 2021;           // change a property

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Looping Through an Object:

for (let key in car) {
  console.log(key + ": " + car[key]);
}

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Object with a Function (Method):

const person = {
  name: "Alice",
  greet: function() {
    console.log("Hello, I'm " + this.name);
  }
};

person.greet(); // Output: Hello, I'm Alice

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this in JavaScript:

The this keyword refers to the object that is currently executing the code.

Its value depends on where and how the function is called.

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Common Cases of this:

1. Inside an Object Method

const person = {
  name: "Alice",
  greet: function() {
    console.log("Hi, I'm " + this.name);
  }
};

person.greet(); // Output: Hi, I'm Alice

Here, this refers to the person object.

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2. In a Regular Function (not in an object)

function show() {
  console.log(this);
}

show(); // In browsers: `this` is the `window` object

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3. In an Event Listener (Browser)

<button onclick="alert(this.innerText)">Click me</button>

this refers to the button that was clicked.

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4. Arrow Functions

const obj = {
  name: "Bob",
  greet: () => {
    console.log("Hello, " + this.name);
  }
};

obj.greet(); // Output: Hello, undefined

Arrow functions do not have their own this — they inherit it from the outer scope.

---# Hoisting in JavaScript:

Hoisting means that JavaScript moves variable and function declarations to the top of their scope (before the code is executed).

But only the declarations are hoisted, not the initializations.

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Example: Variable Hoisting

console.log(x); // undefined
var x = 5;

Behind the scenes, JavaScript treats it like:

var x;
console.log(x); // undefined
x = 5;

var is hoisted — declared at the top, but not assigned.

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let and const Hoisting

console.log(y); // ReferenceError
let y = 10;

• let and const are hoisted, but they are not initialized.
• They stay in a "temporal dead zone" until the line where they are defined.

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Function Hoisting

greet(); // Hello!

function greet() {
  console.log("Hello!");
}

Function declarations are fully hoisted — both the name and the body.

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Function Expressions (NOT Hoisted)

sayHi(); // TypeError: sayHi is not a function

var sayHi = function() {
  console.log("Hi!");
};

• Only the variable sayHi is hoisted (as undefined), not the function.

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Summary Table:

Type	Hoisted?	Usable before definition?
var	Yes (declared)	Yes, but value is undefined
let / const	Yes (declared)	No (ReferenceError)
Function declaration	Yes	Yes
Function expression	Partially	No (TypeError)

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