📌 What Does this Mean in JavaScript?

Simple meaning:

👉 this means “who is calling the function.”

It refers to the object that is executing the function.

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📌 1️⃣ this Inside Normal Functions

Example:

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

show();

In browser:

• this → window object

In strict mode:

• this → undefined

But don’t go deep right now.

Just remember:

👉 In a normal function, this depends on how the function is called.

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📌 2️⃣ this Inside Objects

This is where it becomes useful.

let person = {
  name: "Rahul",
  greet: function() {
    console.log("Hi, I am " + this.name);
  }
};

person.greet();

Output:

Hi, I am Rahul

Why?

Because:

👉 person is calling greet()

So this = person object

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📌 What is call()?

call() lets you borrow a function and set this manually.

---

Example

let person1 = {
  name: "Rahul"
};

let person2 = {
  name: "Aman"
};

function greet() {
  console.log("Hello " + this.name);
}

greet.call(person1); // Hello Rahul
greet.call(person2); // Hello Aman

👉 call() sets who this should be.

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call() with Arguments

function introduce(city) {
  console.log(this.name + " lives in " + city);
}

introduce.call(person1, "Bhopal");

Arguments are passed normally (comma separated).

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📌 What is apply()?

Same as call()

But arguments are passed as an array.

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Example

introduce.apply(person1, ["Delhi"]);

Only difference:

• call() → arguments separated

• apply() → arguments inside array

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📌 What is bind()?

bind() does NOT call the function immediately.

It returns a new function with fixed this.

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Example

let newFunction = introduce.bind(person2);

newFunction("Mumbai");

Output:

Aman lives in Mumbai

👉 bind() stores the connection for later use.

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📊 Difference Between call, apply, bind

Method	Calls Immediately?	Arguments Format	Returns New Function?
call()	✅ Yes	Normal arguments	❌ No
apply()	✅ Yes	Array	❌ No
bind()	❌ No	Normal arguments	✅ Yes

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📊 Diagram Idea – Function → Caller Relationship

Function greet()
       ↑
   Called By
       ↑
   person object
       ↓
   this = person

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🎓 Assignment Practice

1️⃣ Create Object with Method

let student = {
  name: "Aman",
  show: function() {
    console.log("Student: " + this.name);
  }
};

student.show();

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2️⃣ Borrow Method Using call()

let student2 = { name: "Neha" };

student.show.call(student2);

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3️⃣ Use apply()

function introduce(city) {
  console.log(this.name + " lives in " + city);
}

introduce.apply(student2, ["Jaipur"]);

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4️⃣ Use bind()

let boundFunc = introduce.bind(student);

boundFunc("Indore");

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🌟 Final Understanding

• this = who is calling the function

• call() = call now, set this

• apply() = same as call, but array arguments

• bind() = create new function, call later