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JavaScript

JS Basics

JS Variables & Operators

JS Data Types & Conversion

JS Numbers & Math

JS Strings

JS Dates

JS Arrays

JS Control Flow

JS Loops & Iteration

JS Functions

JS Objects

JS Classes & Modules

JS Async Programming

JS Advanced

JS HTML DOM

JS BOM (Browser Object Model)

JS Web APIs

JS AJAX

JS JSON

JS Graphics & Charts

Function Call

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📘 JavaScript call() Method – Function Invocation with Custom Context

The call() method lets you invoke a function, explicitly setting the value of this and passing arguments one by one.

🔹 Syntax

func.call(thisArg, arg1, arg2, ...);

  • thisArg: Value to use as this inside the function.

  • arg1, arg2, ...: Arguments passed individually.

🔹 Example 1 – Basic Usage

function greet(city) {
  console.log(`Hello ${this.name} from ${city}`);
}

const person = { name: "Ravi" };

greet.call(person, "Delhi"); 
// Output: Hello Ravi from Delhi

🔹 Example 2 – Using Call to Borrow Methods

const person1 = {
  name: "Alice",
  greet: function () {
    console.log("Hi " + this.name);
  },
};

const person2 = { name: "Bob" };

person1.greet.call(person2); // Output: Hi Bob

🔹 call() vs apply()

Feature call() apply()
Syntax func.call(this, arg1, arg2) func.apply(this, [arg1, arg2])
Arguments Passed individually Passed as array

Practice Questions

Q1. Write a function sayName(greeting) that prints "greeting, my name is [this.name]". Use call() with { name: "Anjali" } and "Hello" as argument.

Q2. Create a function multiply(x, y) and call it using call() with null as this and numbers 4 and 5 as arguments.

Q3. Create two objects a and b. Let a have a method show() that prints this.value. Use call() to run a.show using b’s context.

Q4. Define a function introduce(city, country) and call it with call() using { name: "Meena" } and arguments "Mumbai", "India". Print a full sentence.

Q5. Create a function area(length, width) and invoke it with call() to calculate and log area of a rectangle.

Q6. Write a function describeRole() that logs this.name + " is a " + this.role. Use call() with two different objects.

Q7. Use a standalone function showBrand() and invoke it with call() using an object { brand: "Nike" } to print the brand.

Q8. Write a function sum(a, b, c) and use call() to pass the values 2, 3, 4 and log the result.

Q9. Create a method showDetails() in object user1 and use call() to reuse it for user2. Both objects should have name and age.

Q10. Create a function combine(first, second) and use call() with an object { separator: " & " } to print "first & second".

Function Call Quiz

Q1: What is the correct syntax for using call()?

A. func.call([args])
B. func.call(thisArg, arg1, arg2)
C. func.call(arg1, arg2, thisArg)
D. func.call(null)

Q2: What does the call() method do?

A. Creates a new object
B. Invokes a function with a specified this and arguments
C. Copies a function to another object
D. Sets a timeout on the function

Q3: What is the main difference between call() and apply()?

A. call() uses comma-separated arguments; apply() uses an array
B. call() is newer than apply()
C. apply() can’t be used with arrow functions
D. call() returns undefined

Q4: Which of the following best describes method borrowing using call()?

A. Using call() to invoke an object's method on another object
B. Copying properties from one object to another
C. Creating a new method
D. Binding a method permanently

Q5: What happens when you call a function using call() with null as this?

A. Causes error
B. this becomes null
C. In non-strict mode, this becomes the global object
D. It won’t execute

Q6: Which is a valid use-case of call()?

A. Setting default arguments
B. Creating classes
C. Borrowing a method from another object
D. Recursively calling a function
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