Creating an object and setting its prototype afterwards

Question

Creating an object and setting its prototype afterwards

While exploring examples and questions online about prototypal inheritance, I noticed that most of them involve assigning prototypes to constructor functions. One common pattern is shown in the code snippet below:

Object.beget = function (o) {
    var F = function () {};
    F.prototype = o;
    return new F();
};

This got me thinking - is there a way to change the prototype of an object (not a constructor function) after it has been instantiated? Essentially, I'm wondering if it's possible to access new prototype methods for an existing object without directly calling them. In simpler terms, can an object inherit new prototype methods post-instantiation?

EDIT:

To clarify my question further, I am not looking to enhance an object's existing prototype. What I really want to achieve is the ability to assign a new prototype to an object, without affecting other objects that share the same initial prototype.

javascript inheritance prototype prototype-programming

Answer 1

Answer №1

Is it possible to modify an object's prototype after it has already been created?

Indeed, there is a way to achieve this: using Object.setPrototypeOf (ES6 only), the counterpart of Object.getPrototypeOf. It allows access to an object's actual prototype, not just the .prototype property. Additionally, there is the deprecated .__proto__ getter/setter property which serves a similar purpose (refer to Quick Javascript inheritance: Understanding __proto__).

Nevertheless, it's important to note that modifying an object's prototype in such a way is generally discouraged. This is not only due to potential lack of support in certain engines, but also because it can negate the performance optimizations that engines apply to instances. For more insights, refer to Why is mutating the [[prototype]] of an object bad for performance?.

Answer 2

Is it possible to modify an object's prototype after it has already been created?

Indeed, there is a way to achieve this: using Object.setPrototypeOf (ES6 only), the counterpart of Object.getPrototypeOf. It allows access to an object's actual prototype, not just the .prototype property. Additionally, there is the deprecated .__proto__ getter/setter property which serves a similar purpose (refer to Quick Javascript inheritance: Understanding __proto__).

Nevertheless, it's important to note that modifying an object's prototype in such a way is generally discouraged. This is not only due to potential lack of support in certain engines, but also because it can negate the performance optimizations that engines apply to instances. For more insights, refer to Why is mutating the [[prototype]] of an object bad for performance?.

Answer 3

Answer №2

By simply using a special function called Object.beget, you can easily assign new properties to your original object, o, and the new object instance will automatically inherit those properties:


Object.beget = function (o) {
    var F = function () {};
    F.prototype = o;
    return new F();
};

var o = {
    a: 1
};

var instance = Object.beget(o);

instance.a === o.a; // true

o.b = function () {};

instance.b === o.b; // true

Answer 4

By simply using a special function called Object.beget, you can easily assign new properties to your original object, o, and the new object instance will automatically inherit those properties:


Object.beget = function (o) {
    var F = function () {};
    F.prototype = o;
    return new F();
};

var o = {
    a: 1
};

var instance = Object.beget(o);

instance.a === o.a; // true

o.b = function () {};

instance.b === o.b; // true

Answer 5

Answer №3

Doesn't it make sense to create a new object with the updated prototype if all the properties inherited from the previous prototype chain need to be removed and new ones added? In that scenario, wouldn't it be more efficient to simply instantiate a new object with the desired prototype?

I would appreciate your insights on any potential overlooked use cases.

Answer 6

Doesn't it make sense to create a new object with the updated prototype if all the properties inherited from the previous prototype chain need to be removed and new ones added? In that scenario, wouldn't it be more efficient to simply instantiate a new object with the desired prototype?

I would appreciate your insights on any potential overlooked use cases.

Creating an object and setting its prototype afterwards

Answer №1

Answer №2

Answer №3

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