What is the process for custom objects to inherit from the JavaScript Object class?

Question

What is the process for custom objects to inherit from the JavaScript Object class?

Can a custom created object access methods like .toString(), which is an Object method? How does a custom class connect to an Object?

According to this article:

All objects ultimately have the Object constructor at the end of their prototype chain. This means any methods or properties added to the Object property are automatically available to all objects.

In the previous example, if we called rufus.toString(), javascript would check the rufus object, then the Cat object, then the Pet object. The Pet object’s prototype was created with the Object constructor (using the object literal shortcut) so javascript would then find the toString() method on the Object’s prototype.

Having read through the article, I now understand that in order to inherit from an object, we need to specify in the prototype of the function constructor of an object the object we want to inherit from. But if the prototype property is empty by default, how can an object have the property toString()? I'm confused about this statement.

The Pet object’s prototype was created with the Object constructor (using the object literal shortcut).

Update:

I learned from this source that the prototype property of the constructor function is empty by default. Here's the quote for reference:

First, every JavaScript function has a prototype property (this property is empty by default), and you attach properties and methods on this prototype property when you want to implement inheritance.

So how exactly do we inherit from the javascript Object then?

javascript

Answer 1

Answer №1

Every object inherits the properties of Object through prototypal inheritance. For instance, if you were to execute:

var b = {};
console.log(b.__proto__)

You would be able to observe all the properties inherited from Object.

Therefore, when you call b.toString(), the program will first search for the toString() function within b. If it is not found there, it will then continue up the prototype chain until it reaches the level of Object where this function exists.

UPDATE:

Comparison Between Function Constructors and Objects:

To clarify further, a function constructor defined as:

var a = function() {
   this.b = "b";
   this.c = "c";
}

will have its prototype linked to function. This linkage can be confirmed by executing console.log(a).

However, we utilize a to create new Objects like so:

var d = new a();

These newly created objects will then have their prototype associated with Object, which can once again be verified using console.log(d).

For further information, please visit this link.

Answer 2

Every object inherits the properties of Object through prototypal inheritance. For instance, if you were to execute:

var b = {};
console.log(b.__proto__)

You would be able to observe all the properties inherited from Object.

Therefore, when you call b.toString(), the program will first search for the toString() function within b. If it is not found there, it will then continue up the prototype chain until it reaches the level of Object where this function exists.

UPDATE:

Comparison Between Function Constructors and Objects:

To clarify further, a function constructor defined as:

var a = function() {
   this.b = "b";
   this.c = "c";
}

will have its prototype linked to function. This linkage can be confirmed by executing console.log(a).

However, we utilize a to create new Objects like so:

var d = new a();

These newly created objects will then have their prototype associated with Object, which can once again be verified using console.log(d).

For further information, please visit this link.

Answer 3

Answer №2

According to the book JavaScript The Definitive Guide:

When objects are created using object literals like {}, they all share the same prototype object referred to in JavaScript code as Object.prototype. On the other hand, objects created using the new keyword with a constructor invocation inherit from the value of the prototype property of the constructor function. Therefore, an object created by new Object() inherits from Object.prototype just like one created by {}. Similarly, new Array() uses Array.prototype as its prototype and new Date() uses Date.prototype.

This means that objects created using {} literals will have Object.prototype as their prototype, allowing them access to methods defined by Object.prototype such as toString().

The role of the new operator is to create and initialize new objects. It must be used in conjunction with a function invocation, known as a constructor invocation when used this way.

Objects created through new and function invocations inherit from the constructors' prototype property. For instance, objects made with new Date() inherit from Date.prototype and those from new Array() inherit from Array.prototype.

If desired, you can modify the prototype property for custom inheritance. For example:

function myFunction() {
    this.name = 'a';
    this.age = 20;
}

myFunction.prototype = {
    toString: function() {
        // custom implementation of toString() method here
    },

    // additional functions can be defined here
};

var myObj = new myFunction();

Object myObj will inherit from myFunction.prototype, granting access to all methods defined within the object.

In EcmaScript5, a new method called Object.create() allows the creation of objects with prototypes other than Object.prototype. For example:

var prototypeObject = {a: 1, b: 2, c: 3};
var obj1 = Object.create(prototypeObject);

Now, obj1 will inherit from prototypeObject rather than Object.prototype.

Answer 4

According to the book JavaScript The Definitive Guide:

When objects are created using object literals like {}, they all share the same prototype object referred to in JavaScript code as Object.prototype. On the other hand, objects created using the new keyword with a constructor invocation inherit from the value of the prototype property of the constructor function. Therefore, an object created by new Object() inherits from Object.prototype just like one created by {}. Similarly, new Array() uses Array.prototype as its prototype and new Date() uses Date.prototype.

This means that objects created using {} literals will have Object.prototype as their prototype, allowing them access to methods defined by Object.prototype such as toString().

The role of the new operator is to create and initialize new objects. It must be used in conjunction with a function invocation, known as a constructor invocation when used this way.

Objects created through new and function invocations inherit from the constructors' prototype property. For instance, objects made with new Date() inherit from Date.prototype and those from new Array() inherit from Array.prototype.

If desired, you can modify the prototype property for custom inheritance. For example:

function myFunction() {
    this.name = 'a';
    this.age = 20;
}

myFunction.prototype = {
    toString: function() {
        // custom implementation of toString() method here
    },

    // additional functions can be defined here
};

var myObj = new myFunction();

Object myObj will inherit from myFunction.prototype, granting access to all methods defined within the object.

In EcmaScript5, a new method called Object.create() allows the creation of objects with prototypes other than Object.prototype. For example:

var prototypeObject = {a: 1, b: 2, c: 3};
var obj1 = Object.create(prototypeObject);

Now, obj1 will inherit from prototypeObject rather than Object.prototype.

Answer 5

Answer №3

You inquired

How can a custom object access methods like the .toString() method, which is part of the Object class? How does a custom class connect to an Object?

It seems like you might have overcomplicated things when thinking about this. You had it figured out, and then you second-guessed yourself. To address your question without delving into code...

In programming, all objects inherit from a default object, acting as a sort of "template" in JavaScript. This base object has fundamental properties and methods that serve as a foundation for all other objects to build upon. Each object may have its own unique set of base properties. While I previously mentioned that the prototype chain ends here, it is more accurate to say that the chain ultimately reaches null.

Answer 6

You inquired

How can a custom object access methods like the .toString() method, which is part of the Object class? How does a custom class connect to an Object?

It seems like you might have overcomplicated things when thinking about this. You had it figured out, and then you second-guessed yourself. To address your question without delving into code...

In programming, all objects inherit from a default object, acting as a sort of "template" in JavaScript. This base object has fundamental properties and methods that serve as a foundation for all other objects to build upon. Each object may have its own unique set of base properties. While I previously mentioned that the prototype chain ends here, it is more accurate to say that the chain ultimately reaches null.

What is the process for custom objects to inherit from the JavaScript Object class?

Answer №1

Answer №2

Answer №3

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