Call.md

call() method

The call() method in JavaScript is a method that is used to call another function, with a given this value and arguments provided individually (not as an array). It is used for function borrowing and for invoking a function with a specific this context.

Here's how it works:

1. It is a method available on all functions.
2. It calls the function with a given this value and arguments provided individually.
3. It returns the result of the function call.

Here's a simple example:

let car1 = {
    color: "Red",
    company: "Ferrari"
}

let car2 = {
    color: "Blue",
    company: "BMW"
}

function purchaseCar(price){
    console.log(`I have purchased ${this.color} ${this.company} for Rs. ${price}`)
}

purchaseCar.apply(car1, "70 lakh") // Output: I have purchased Red Ferrari for Rs. 70 lakh
purchaseCar.apply(car2, "90 lakh") // Output: I have purchased Blue BMW for Rs. 90 lakh

In this example, call() is called on the purchaseCar function with car1 as the this value. It calls purchaseCar with this set to car1, so this.color and this.company inside purchaseCar refer to car1.color and car1.company, respectively. The purchaseCar function is not changed. Similar happens when call() is called on the purchaseCar function with car2 as the this value. This time the this refers to car2, therefore the same purchaseCar function can be borrowed by both the objects car1 and car2. Also the arguments passed to the function purchaseCar are not provided as array, this is the only difference between call() and apply() method.

Syntax

The syntax for the call() method in JavaScript is as follows:

function.call(thisObj, arg1, arg2, ...)

Here's what each parameter means:

• thisObj: The value of this provided for the call to function. Note that this may not be the actual value seen by the method: if the method is a function in non-strict mode, null and undefined will be replaced with the global object, and primitive values will be boxed.

• arg1, arg2, ...: Arguments for the object method. They are optional and can be passed individually to the function.

Polyfill

Function.prototype.call = function(context, ...args) {

    context.fn = this;

    context.fn(...args);

};