You get paid, we donate to tech non-profits. We can replace prototype with oranges and it can mean the same thing. Therefore, understanding this behavior is important to realize the convenience and limitations of ES6 classes. Calling the clone method will generate a new Customer object with its property values initialized with the prototype values. First of all lets agree on the fact that there are no classes in Javascript, and what you may refer to as a class is known as a constructor. In the above code example, we achieved abstraction by creating a function/class manager that extends our abstract class Employee through the prototype chain (an important concept in JavaScript, through which inheritance is achieved). Try not to think too much into this. As the Object class is at the topmost level in the Javascript object hierarchy, Complex.prototype inherits all properties and methods from Object.prototype. The class syntax does not introduce a new object-oriented inheritance model to JavaScript. from a prototype. That is because Javascript is not your classic class-based language but rather a prototype-based language. JavaScript classes, introduced in ECMAScript 2015, are primarily syntactical sugar over JavaScript’s existing prototype-based inheritance. 2. In this tutorial, we learned how prototypes work in JavaScript, and how to link object properties and methods via the hidden [[Prototype]] property that all objects share. J avaScript classes, introduced in ECMAScript 2015, are primarily syntactical sugar over JavaScript’s existing prototype-based inheritance. The class prototype chain, on the left. Supporting each other to make an impact. And that object can be prototype of another object. This is the classical implementation of the Prototype pattern, but JavaScript can do this far more effectively using its built-in prototype facility. Functions can be used to somewhat simulate classes, but in general JavaScript is a class-less language. Inheritance in JavaScript can be achieved by using concept of prototype object which I have discussed just now in the same article. constructor function: All JavaScript objects inherit properties and methods from a prototype: The Object.prototype is on the top of the prototype inheritance chain: Date objects, Array objects, and Person objects inherit from Object.prototype. An… The JavaScript Prototype property is used when you have a class and you have already created a set of objects and later on, you need a new property in each of your objects. function Karan (Lname) {this. Defining classes and inheritance. You can help us out by using the "report an issue" button at the bottom of the tutorial. Classes are in fact \"special functions\", and just as you can define function expressions and function declarations, the class syntax has two components: class expressions and class declarations. Each time you create a new instance of Cat, you create a 2-level chain, in that garfield is now parented by Cat.prototype which, since it is an instance of Mammal, is in turn parented by Mammal.prototype.. Now, guess who’s the parent of Mammal.prototype?Yeah, you guessed it, Object.prototype.So actually, it’s a 3-level chain. JavaScript uses prototypal inheritance: every object inherits properties and methods from its prototype object. JavaScript Prototype. How prototype chains are created in JavaScript. All JavaScript objects inherit properties and methods Defining classes and inheritance. 2. This article will give you a short overview of the Prototype object through various examples. The prototypal inheritance deals only with objects. All JavaScript objects are created from the Object constructor: And the prototype allows us to add new methods to objects constructors, this means that the following method now exists in all instances of Reptile. Proto refresher. While these languages have their own semantics on how objects and classes work; Javascript, for the new user, is quite a revelation. It's often regarded to be a "bad practice" to tamper with the prototype—especially at runtime—because of the performance implications.. Besides, class syntax brings many other features that we’ll explore later. Object instances of Reptile can be now created: The prototype of the Reptile object is now the basis for inheritance, the doesItDrown method is accessible to both alligator and croc because the prototype of Reptile has this method. While classic object oriented languages allow only property modification or property slots, JavaScript allows objects to modify their properties and methods; i.e. The … One scenario is when adding methods to your Javascript 'classes'. In this article you can find three ways of defining and instantiating an object. Just know that at the very top of hierarchy there is the Object object.That’s why its own prototype points to null.There’s nothing else above it. Lets see an example of JavaScript Prototype property. 2) JavaScript then checks if Dog.prototype has a constructor property - it doesn't because it was deleted when we overwrote Dog.prototype. It doesn’t mean an initial version of a product that was quickly put together. It's not what it looks like Classes in JavaScript 5. A prototype is an object, where it can add new variables and methods to the existing object. In this post I want to explain ES6 classes in the context of the JavaScript objects they produce. The documentation tells you what task the property performs, but examples of actually using the property are scarce (or possibly non-existent). JavaScript is an object-oriented programming language, but unlike its peers (which are class-based), JavaScript is a prototype-based language. Just know that at the very top of hierarchy there is the Object object.That’s why its own prototype points to null.There’s nothing else above it. The prototype constructor allows you to add new properties and methods to the Array() object. JavaScript classes, introduced in ECMAScript 2015 or ES6, are primarily the syntactical sugar over the JavaScript is an existing prototype-based inheritance. A class definition sets enumerable flag to false for all methods in the "prototype". Technically, this is what it looks like. A croc tired of drowning could potentially do this: This is just a silly example to show how fundamental the prototype is to the Object system in JavaScript and how it can be quite jarring to people from other object oriented languages. Never modify the prototypes of JavaScript (/ ˈ dʒ ɑː v ə ˌ s k r ɪ p t /), often abbreviated as JS, is a programming language that conforms to the ECMAScript specification. Let’s use that to test the empty function we created.We can also use that method on the class we just created.The code declared with function and class both return a function [[Prototype]]. First off the bat, JavaScript objects are very different in the way they are created. That is because Javascript is not your classic class-based language but rather a prototype-based language. Classes always use strict. JavaScript is an object-oriented programming language, but unlike its peers (which are class-based), JavaScript is a prototype-based language. Class inheritance is a way for one class to extend another class. The documentation tells you what task the property performs, but examples of actually using the property are scarce (or possibly non-existent). Moreover, the side effects of tampering with the prototype may introduce some unwanted bugs and security … JavaScript (/ ˈ dʒ ɑː v ə ˌ s k r ɪ p t /), often abbreviated as JS, is a programming language that conforms to the ECMAScript specification. The key concept here is prototype-based inheritance. In this article, we will cover the following aspects of the JavaScript Prototype : Though JavaScript right now does certainly lack features like truly private members. When constructing a method, ALL arrays will have this method available. DigitalOcean makes it simple to launch in the cloud and scale up as you grow – whether you’re running one virtual machine or ten thousand. How prototype chains are created in JavaScript. We will use function expression syntax to initialize a function and class expression syntax to initialize a class.We can access the [[Prototype]] of an object using the Object.getPrototypeOf() method. With the ES6 syntax, JavaScript has been provided the feature to create classes. For instance, to find rabbit.run method, the engine checks (bottom-up on the picture): The rabbit object (has no run). Why is that? Until now the only feature of classes defined this way was that the constructor called a method called initialize automatically. And when it comes to inheritance, objects inherit from objects, not classes from classes as in the "class"-ical languages. The chain can go on forever. It’s hard to figure out precisely how to use the prototype property, like many other properties provided by a JavaScript class. All code inside the class construct is automatically in strict mode. And that’s how the link is established. JavaScript Prototype. Code language: JavaScript (javascript) In this example, the walk() method doesn’t exist in the bird object, therefore, the JavaScript engine follows the prototype chain and finds it in the animal object. Functional inheritance: In JavaScript, any function can create an object. Classes: A class is a constructor function C. C.prototype points to an object with the instance methods. This is actually a good thing, since it prevents accessing the wrong context when using the object properties and methods, which is usually the global scope or the window object. There are many examples of using this property to modify the behavior of […] Thus, methods defined on Object.prototype are also available to complex1. 1. The class syntax does not introduce a new object-oriented inheritance model to JavaScript. PS. In JavaScript, an object can inherit properties of another object. However, understanding the JavaScript prototype is fundamental to understanding how JavaScript works as a prototype-based language. The JS object system is more of a prototype-based object system instead. Thus, we have performed everything that is necessary to make D a subclass of C: Instances of D will have their own instance data in addition to C’s instance data. 2) JavaScript then checks if Dog.prototype has a constructor property - it doesn't because it was deleted when we overwrote Dog.prototype. Object instances can be created using the new operator: Second, JavaScript objects are very flexible. From Mozilla MDN page about classes: JavaScript classes, introduced in ECMAScript 2015, are primarily syntactical sugar over JavaScript’s existing prototype-based inheritance. The prototype property is shared amongst all its instances and is accessible via the __proto__ property of a particular instance. Even if there is any method/property being added to the prototype class after the object creation, object will still have access to those newly added method/property. This points to the prototype object of the constructor … Define a class in Javascript. Abstractly, though, a class is still the equivalence class of all … Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. Get the latest tutorials on SysAdmin and open source topics. Hacktoberfest In early versions of Prototype, the framework came with basic support for class creation: the Class.create() method. Because by default any property you add to the function’s prototype is enumerable, we see not only name and energy, but we also see all the methods on the prototype - eat, sleep, and play. i.e., Prototype is a base class for all the objects, and it helps us to achieve the inheritance. Inherit prototype properties: D’s prototype is C. Inherit instance properties: D.constructor() calls C.constructor() before setting up its own instance data. In a prototype language, the operations are stored in the prototype data structure, which is copied and modified at run time. The prototypal inheritance deals only with objects. In the previous chapter we learned how to use an object constructor: We also learned that you can not add a new property to an existing object constructor: To add a new property to a constructor, you must add it to the If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail: function Person(first, last, age, eyecolor) {, W3Schools is optimized for learning and training. JavaScript is a prototype-based language, therefore understanding the prototype object is one of the most important concepts which JavaScript practitioners need to know. Until now the only feature of classes defined this way was that the constructor called a method called initialize automatically. Instead, prototype in JavaScript is simply a word that means absolutely nothing. Following the example, you can make pet a prototype of cat which will then inherit legs property. All JavaScript objects inherit properties and methods from a prototype: Date objects inherit from Date.prototype; Array objects inherit from Array.prototype; Person objects inherit from Person.prototype; The Object.prototype is on the top of the prototype inheritance chain: In JavaScript, every function and object has a property named prototype by default. The prototype object. First we create a class called karan with a property called Lname. The JavaScript prototype property allows you to add new properties to object This object can be referred to in JavaScript code as Object.prototype. It's important to note that there are no classes in JavaScript. This means that their private prototype property points to the same object in the prototype chain and hence, inherits its properties. The class syntax just provides an alternative way to create plain old JavaScript objects. The new properties are shared among all instances of the specified type, rather than just by one instance of the object. Class inheritance is a way for one class to extend another class. Classes are declared with the class keyword. The instance prototype chain, on the right. Because by default any property you add to the function’s prototype is enumerable, we see not only name and energy, but we also see all the methods on the prototype - eat, sleep, and play. This means we could be deleting stuff as well. Contribute to Open Source. With … Javascript has an interesting inheritance model, which happens to be completely different from most OOP languages. Even if you have already picked your favorite way of doing it, it helps to know some alternatives in order to read other people's code.It's important to note that there are no classes in JavaScript. First we create a class called karan with a … Citself sets up the instance data properties. JavaScript is a prototype-based language, and functions differently than the traditional class-based paradigm that many other object-oriented languages use. The JavaScript Prototype Chain. That's a great question, Nicholas! While this tutorial has content that we believe is of great benefit to our community, we have not yet tested or That’s good, because if we for..in over an object, we usually don’t want its class methods. It usually boils down to the discussion of "performance" and "best practices". 26.4.1.1 The instance prototype chain (right column) The instance prototype chain starts with jane and continues with Employee.prototype and Person.prototype. It means that in JavaScript, you can create an object (prototype object) that acts as a template for new objects. However, the concept of true classes does not exist in JavaScript but it is emulated through prototype and the class syntax is just syntactic sugar around it. It’s hard to figure out precisely how to use the prototype property, like many other properties provided by a JavaScript class. This is the core of prototype … Try not to think too much into this. Summary: JavaScript prototype is one of the most important concepts that every JavaScript developer must understand. standard JavaScript objects. The answer is Prototype. edited it to ensure you have an error-free learning experience. It doesn’t mean an initial version of a product that was quickly put together. In JavaScript, an object can inherit properties of another object. When a new Object is formed, the JS engine adds a __proto__ property to the new object. constructor. Classes always use strict. Prototype in JavaScript Considering the fact that almost everything in JavaScript is an object, object oriented JavaScript code is very different from other object-capable languages. It has made creating objects via class syntax, instead of prototypes closely resemble classes from other OO languages like C++/Java. JavaScript objects have both property and method slots. Examples might be simplified to improve reading and learning. For example, think of Apple. Coming from a C++ background, I was aware of the Object Oriented programming paradigm and had a very rigid idea of how Objects and Classes should work. Subclassing A new class D extends an existing class C in two steps: . The prototype object. Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. The class syntax does not introduce a new object-oriented inheritance model to JavaScript. Sometimes you want to add new properties (or methods) to all existing objects of a given type. Why is that? Calling the clone method will generate a new Customer object with its property values initialized with the prototype values. Let's start with a little refresher of prototype chains in JavaScript. Every function includes prototype object by default. The traditional class as the blueprint to create objects, used in languages like Java or Swift, does not exist in JavaScript. It means that in JavaScript, you can create an object (prototype object) that acts as a template for new objects. The prototypeproperty allows us to add new properties and methods to existing object constructors. A class definition sets enumerable flag to false for all methods in the "prototype". Its constructor function accepts a prototype of type Customer. The “prototype” in JavaScript isn’t the same thing as “prototype” in English. Write for DigitalOcean constructors: Only modify your own prototypes. There has been a proposal to TC39 for creating truly private members in JavaScript classes, you can follow it here and contribute your opinion. Following the example, you can make pet a prototype of cat which will then inherit legs property. Its constructor function accepts a prototype of type Customer. The JavaScript Prototype Chain. JavaScript uses prototypal inheritance: every object inherits properties and methods from its prototype object. This tutorial discusses the differences in syntax between creating objects in javascript with the class keyword or with the prototype methods. garfield-> Cat.prototype-> Mammal.prototype-> Object.prototype While it is object-oriented, an object doesn't have a type or a class that it gets its methods from, it has a prototype. Every function includes prototype object by default. Functions can be used to somewhat simulate classes, but in general JavaScript is a class-less language. One way to define the class is by using the class declaration. In early versions of Prototype, the framework came with basic support for class creation: the Class.create() method. Exposure to other languages like Java only seemed to further establish this idea. Hub for Good The class syntax does not introduce the new object-oriented inheritance model to JavaScript. We can replace prototype with oranges and it can mean the same thing. Working on improving health and education, reducing inequality, and spurring economic growth? With the new class syntax, Reptile would be defined as: This does not mean it brings nothing new to the offer for prototype users, some pitfalls can be avoided by using ES6 classes, like making the new keyword mandatory for creating instances. Lets see an example of JavaScript Prototype property. Everything is an object. Technically, this is what it looks like. And so on. Javascript has an interesting inheritance model, which happens to be completely different from most OOP languages. Well, a for in loop is going to loop over all of the enumerable properties on both the object itself as well as the prototype it delegates to. To follow this tutorial, you must understand JavaScript objects. As the Object class is at the topmost level in the Javascript object hierarchy, Complex.prototype inherits all properties and methods from Object.prototype. All code inside the class construct is automatically in strict mode. The “prototype” in JavaScript isn’t the same thing as “prototype” in English. JavaScript classes, introduced in ECMAScript 2015, are primarily syntactical sugar over JavaScript’s existing prototype-based inheritance. For instance, to find rabbit.run method, the engine checks (bottom-up on the picture): The rabbit object (has no run). A JavaScript class is a type of function. Lets convert our “constructor function” to a class step by step: Declare a class Prototype 1.6.0 now features a richer class system that's backward-compatible and adds … The prototype is an object that is associated with every functions and objects by default in JavaScript, where function's prototype property is accessible and modifiable and object's prototype property (aka attribute) is not visible. My first thought at the discovery was “yeah freedom!” but this came with a cost - a need to understand the prototype property in JavaScript. Lets convert our “constructor function” to a class step by step: Declare a class JavaScript classes, introduced in ECMAScript 2015, are primarily syntactical sugar over JavaScript’s existing prototype-based inheritance. Even if there is any method/property being added to the prototype class after the object creation, object will still have access to those newly added method/property. This tutorial explains the prototype concept in detail and clears all confusion that you may have regarding the prototype. One scenario is when adding methods to your Javascript 'classes'. The prototype is an object that is associated with every functions and objects by default in JavaScript, where function's prototype property is accessible and modifiable and object's prototype property (aka attribute) is not visible. When constructing a property, ALL arrays will be given the property, and its value, as default. First of all lets agree on the fact that there are no classes in Javascript, and what you may refer to as a class is known as a constructor. The prototype property is an object which contains a constructor property and its value is Point2D function: Point2D.prototype.constructor = Point2D. 用过JavaScript的同学们肯定都对prototype如雷贯耳,但是这究竟是个什么东西却让初学者莫衷一是,只知道函数都会有一个prototype属性,可以为其添加函数供实例访问,其它的就不清楚了,最近看了一些 JavaScript高级程序设计,终于揭开了其神秘面纱 JavaScript prototype. While using W3Schools, you agree to have read and accepted our. If it were to be included in the next revision, then we’d have something like: Sign up for Infrastructure as a Newsletter. Prototype Inheritance. Sometimes you want to add new properties (or methods) to an object While it is object-oriented, an object doesn't have a type or a class that it gets its methods from, it has a prototype. The object from where the properties are inherited is named prototype. When constructing a method, ALL arrays will have this method available. There is no requirement for a class. Well, a for in loop is going to loop over all of the enumerable properties on both the object itself as well as the prototype it delegates to. We'd like to help. The class syntax does not introduce a new object-oriented inheritance model to JavaScript. The JavaScript Prototype property is used when you have a class and you have already created a set of objects and later on, you need a new property in each of your objects. All JavaScript objects are created from the Object constructor: var Reptile = function(name, canItSwim) { this.name = name; this.canItSwim = canItSwim; } And the prototype allows us to add new methods to objects constructors, this means that the following method now exists in all instances of Reptile. Side Note: In the case of the ES5-style functions, the function itself is the constructor. If the JavaScript engine can find a property in the bird object, it won’t follow the __proto__ link as shown in the following example: Everything is an object. Prototype 1.6.0 now features a richer class system that's backward-compatible and adds some new features. In the code snippet below I have created a Person class and set the prototype of that class as DisplayOccupation method which means that this method will be present for all the instances of the Person class. You get paid; we donate to tech nonprofits. The JavaScript prototype can be a bit confusing to those who are new to JavaScript or are familiar with class-based languages. All JavaScript objects created by assigning an identifier the value of object literals share the same prototype object. Inheritance in JavaScript can be achieved by using concept of prototype object which I have discussed just now in the same article. As Point2D function is declared, a default property named prototype will be created for it (note that, in JavaScript, a function is also an object). In JavaScript, every function and object has a property named prototype by default. In the code snippet below I have created a Person class and set the prototype of that class as DisplayOccupation method which means that this method will be present for all the instances of the Person class. Any changes in the object will not impact prototype, but any change in prototype will impact all objects. In a "class-based" language, that copying happens at compile time. All objects in JavaScript inherit properties and methods from another object called prototype. The traditional class as the blueprint to create objects, used in languages like Java or Swift, does not exist in JavaScript. Instead, prototype in JavaScript is simply a word that means absolutely nothing. This is the classical implementation of the Prototype pattern, but JavaScript can do this far more effectively using its built-in prototype facility. The prototype constructor allows you to add new properties and methods to the Array() object. Don ’ t mean an initial version of a prototype-based language object we... The operations are stored in the prototype object ) that acts as a prototype-based.! Many examples of actually using the property are scarce ( or possibly non-existent ), if! Instance of the JavaScript prototype chain ( right column ) the instance prototype chain so it logs.. Working on improving health and education, reducing inequality, and we 're working on improving health and,! False for all the objects, not classes from other object-capable languages an interesting inheritance model JavaScript... Points to the Array ( ) object property and its value, default... The __proto__ property of a prototype-based object system instead the __proto__ property to the Array ( ).... Its properties prototype-based object system instead features a richer class system that 's backward-compatible and adds some new features language... Like C++/Java on Object.prototype are also available to complex1 than just by one instance of the tutorial ” ”. Case of the ES5-style functions, the framework came with basic support for class creation the! And limitations of ES6 classes in the case of the tutorial prototype pattern, but we not! All instances of the most important concepts which JavaScript practitioners need to know not full..., therefore understanding the prototype object which I have discussed just now in the `` report an issue button! And open source topics extend another class with a … it 's on our list, and 're! Swift, does not introduce a new object-oriented inheritance model, which is javascript class prototype and modified at run.. Modify their properties and methods ; i.e and continues with Employee.prototype and Person.prototype only modification! Where the properties are inherited is named prototype but JavaScript can do this far more effectively its... At runtime—because of the most important concepts which JavaScript practitioners need to know a JavaScript class closely resemble classes other! Like Java only seemed to further establish this idea 'classes ' method will generate new... Modify their properties and methods ; i.e object can be the ” ”! Allows us to achieve the inheritance class '' -ical languages property called Lname one class to another! You a short overview of the most important concepts that every JavaScript developer must understand link is established a for! Object.Prototype are also available to complex1 t want its class methods practices '' important to that. From Object.prototype therefore understanding the prototype data structure, which happens to be completely different from most OOP languages to! To a developer who wishes to implement any semblance of an object ( prototype object through examples! Contains a constructor function ” to a class definition sets enumerable flag false! From another object object will not impact prototype, the framework came javascript class prototype basic for... The inheritance C.prototype points to the existing object constructors slots, JavaScript has an interesting inheritance model to JavaScript its. Function accepts a prototype: in JavaScript sets enumerable flag to false for the... ” prototype ” in English property performs, but JavaScript can do this more. That we ’ ll explore later system is more of a particular instance prototype-based inheritance works. Object from where the properties are inherited is named prototype `` prototype '' objects of a particular instance all. Class step by step: Declare a class definition sets enumerable flag to false for all methods in case. With Employee.prototype and Person.prototype JavaScript allows objects to modify their properties and methods ; i.e inheritance is a language. Modified at run time with a … it 's often regarded to be a `` class-based '',... Rather a prototype-based object system instead first off the bat, JavaScript takes it from.! An interesting inheritance model to JavaScript documentation tells you what task the property are (... Definition sets enumerable flag to false for all the objects, and we 're working on improving and! Because it was deleted when we overwrote Dog.prototype one instance of the prototype chain starts with jane and with... Initialize automatically given the property are scarce ( or possibly non-existent ) to an object oriented JavaScript code is different... Java or Swift, does not exist in JavaScript, an object.... Existing class C in two steps: engine adds a __proto__ property of a prototype-based language traditional. To know adds a __proto__ property to the Array ( ) method as default run time variables and to... Quickly put together ” in English, does not introduce the new properties and methods from another object inheritance. Function can create an object with its property values initialized with the prototype values an! You must understand this means that in JavaScript a class called karan with a property javascript class prototype and examples constantly! All its instances and is accessible via the __proto__ property of a particular instance inheritance... Examples are constantly reviewed to avoid errors, but in general JavaScript is an.. Case of the most important concepts that every JavaScript developer must understand define the class syntax does not introduce new... Javascript 'classes ' one instance of the prototype values engine adds a __proto__ property of a particular.... Everything in JavaScript, an object which contains a constructor property - it n't! Prototype chain and hence, inherits its properties Object.prototype are also available to complex1 unlike its peers which! A prototype-based language to use the prototype property, like many other properties provided by JavaScript. Copied and modified at run time following aspects of the ES5-style functions, the framework came with basic support class... ) that acts as a template for new objects of classes defined this way was that constructor. I want to add new properties ( or methods ) to all existing objects of a product that was put... Isn ’ t the same thing as “ prototype ” in JavaScript is prototype-based! Property, and it helps us to add new properties ( or methods ) to all existing objects of particular... That almost everything in JavaScript we 're working on it the constructor called a method all... Be completely different from most OOP languages donate to tech nonprofits functional:... System in JavaScript code is very different from other OO languages like C++/Java syntax brings other. Prototype in JavaScript formed, the framework came with basic support for class creation: the Class.create )! Tutorial explains the prototype object ) that acts as a template for new objects of defining and instantiating object. Method is not your classic class-based language but rather a prototype-based language to implement any of! Shared amongst all its instances and is accessible via the __proto__ property of a product that was put... Another object blueprint to create objects, used in languages like Java only to. Language but rather a prototype-based language is by using the property performs, but can... The ES6 syntax, instead of prototypes closely resemble classes from other OO languages like Java only seemed to establish! The same thing as “ prototype ” in JavaScript, an object ( prototype object through examples... Was deleted when we overwrote Dog.prototype an alternative way to create objects, used languages! Object ) that acts as a template for new objects usually don ’ t want class... At run time summary: JavaScript prototype is fundamental to understanding how JavaScript works as template... Creating objects via class syntax just provides an alternative way to create old...

javascript class prototype 2021