Interview question

What is the difference between proto and prototype? proto और prototype में क्या अंतर है?

Answer

Property	Exists on	Purpose
prototype	Functions (specifically constructor functions/classes)	The object that will become the __proto__ of instances created with 'new'
__proto__	Every object instance	The actual link to that object's prototype (accessor for the internal [[Prototype]])

function Person(name) {
    this.name = name;
}
Person.prototype.greet = function() {
    return `Hi, I'm ${this.name}`;
};

const john = new Person('John');

// Person.prototype is the blueprint object
console.log(typeof Person.prototype); // 'object'

// john.__proto__ points to Person.prototype
console.log(john.__proto__ === Person.prototype); // true

// This is how john can access greet() even though it's not john's own property
console.log(john.hasOwnProperty('greet')); // false
console.log(john.greet()); // Hi, I'm John - found via __proto__ chain

// Modern way to get/set the prototype (preferred over direct __proto__ access)
console.log(Object.getPrototypeOf(john) === Person.prototype); // true
Object.setPrototypeOf(john, Person.prototype); // equivalent to john.__proto__ = ...

// Functions themselves have BOTH a prototype property AND a __proto__
console.log(typeof Person.prototype);       // 'object' - used by 'new'
console.log(Person.__proto__ === Function.prototype); // true - Person is itself an object/function

// Only functions (used as constructors) have a meaningful .prototype property
console.log(john.prototype); // undefined - john is not a function

Property	किस पर है	उद्देश्य
prototype	Functions (constructor functions/classes)	'new' से बने instances का __proto__ बनने वाला object
__proto__	हर object instance	उस object के prototype का actual link

function Person(name) {
    this.name = name;
}
Person.prototype.greet = function() {
    return `Hi, I'm ${this.name}`;
};

const john = new Person('John');

console.log(typeof Person.prototype); // 'object'

// john.__proto__ Person.prototype की ओर point करता है
console.log(john.__proto__ === Person.prototype); // true

console.log(john.hasOwnProperty('greet')); // false
console.log(john.greet()); // Hi, I'm John

// Modern तरीका
console.log(Object.getPrototypeOf(john) === Person.prototype); // true
Object.setPrototypeOf(john, Person.prototype);

// Functions में दोनों होते हैं
console.log(typeof Person.prototype);
console.log(Person.__proto__ === Function.prototype); // true

// सिर्फ functions के पास meaningful .prototype होता है
console.log(john.prototype); // undefined

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