Prototypal Inheritance
Douglas Crockford www.crockford.com Five years ago I wrote Classical Inheritance in JavaScript (Chinese Italian Japanese). It showed that JavaScript is a class-free, prototypal language, and that it has sufficient expressive power to simulate a classical system. My journey was circuitous because JavaScript itself is conflicted about its prototypal nature. new () produces a new object that inherits from .prototype This indirection was intended to make the language seem more familiar to classically trained programmers, but failed to do that, as we can see from the very low opinion Java programmers have of JavaScript. Fortunately, it is easy to create an operator that implements true prototypal inheritance. function object(o) { function F() {} F.prototype = o; return new F(); } The object function untangles JavaScript's constructor pattern, achieving true prototypal inheritance. So instead of creating classes, you make prototype objects, and then use the object function to make new instances.
Understanding JavaScript Prototypes.
(en Español, русском, 中文) JavaScript’s prototype object generates confusion wherever it goes. Seasoned JavaScript professionals, even authors frequently exhibit a limited understanding of the concept. What is a prototype? A prototype is an object from which other objects inherit properties Can any object be a prototype? Yes. Which objects have prototypes? Every object has a prototype by default. OK back up, what is an object again? An object in JavaScript is any unordered collection of key-value pairs. You said every object has a prototype. Forget everything you learned about the prototype property – it’s probably the biggest source of confusion about prototypes. Ok fine, but false is a primitive, so why does false. When a primitive is asked for it’s prototype it will be coerced to an object. I want to use prototypes for inheritance. But the real power of prototype is seen when multiple instances share a common prototype. So is this where constructors come in? Yes. OK. Example please? Like this:
Introduction to Object-Oriented JavaScript
Object-oriented to the core, JavaScript features powerful, flexible OOP capabilities. This article starts with an introduction to object-oriented programming, then reviews the JavaScript object model, and finally demonstrates concepts of object-oriented programming in JavaScript. This article does not describe the newer syntax for object-oriented programming in ECMAScript 6. JavaScript review If you don't feel confident about JavaScript concepts such as variables, types, functions, and scope, you can read about those topics in A re-introduction to JavaScript. Object-oriented programming Object-oriented programming (OOP) is a programming paradigm that uses abstraction to create models based on the real world. OOP envisions software as a collection of cooperating objects rather than a collection of functions or simply a list of commands (as is the traditional view). Terminology Namespace A container which lets developers bundle all functionality under a unique, application-specific name. Class
Using Prototypes in Javascript | TimKadlec.com
As mentioned in my previous post, I think using prototypes is powerful enough to deserve a more detailed explanation. To start off, let me say we are talking about the prototype method here, not the JavaScript library. Prototypes allow you to easily define methods to all instances of a particular object. The beauty is that the method is applied to the prototype, so it is only stored in the memory once, but every instance of the object has access to it. Let’s use the Pet object that we created in the previous post. function Pet(name, species){ this.name = name; this.species = species;}function view(){ return this.name + " is a " + this.species + "!" As you can see, by using simply using prototype when we attached the view method, we have ensured that all Pet objects have access to the view method. function Pet(name, species){ this.name = name; this.species = species;}function view(){ return this.name + " is a " + this.species + "!"
Using Prototype Property in JavaScript
Exclusive offer: get 50% off this eBook here Object-Oriented JavaScript — Save 50% Create scalable, reusable high-quality JavaScript applications and libraries by Stoyan Stefanov | August 2008 | AJAX Web Development In this article by Stoyan Stefanov, you'll learn about the prototype property of the function objects. The following topics are discussed in this article: Every function has a prototype property and it contains an objectAdding properties to the prototype objectUsing the properties added to the prototypeThe difference between own properties and properties of the prototype__proto__, the secret link every object keeps to its prototypeMethods such as isPrototypeOf(), hasOwnProperty(), and propertyIsEnumerable() The functions in JavaScript are objects and they contain methods and properties. If you define a simple function foo() you can access its properties as you would do with any other object: >>>function foo(a, b){return a * b;}>>>foo.length >>>foo.constructor Function() "object" "foo"
Constructores en Javascript considerados ligeramente confusos
Traducido del Original en el blog code.h(oe)kje. Considerando la afirmación de Flanagan 2006, (página 111) que aparece en una pregunta de comp.lang.javascript el mes pasado: En javascript, cada objeto tiene una propiedad constructor que se refiere a la función constructor que inicializa el objeto. Suena bien: hace que los constructores parezcan estáticos como las clases en Java. Incluso la sintaxis new Constructor() parece igual: Pero la vida no es tan simple: ¿Qué pasa? Objetos y métodos Los objetos en Javascript son simples bolsas de propiedades con nombre que pueden ser leidas y escritas. Las funciones en javascript son objetos de primera clase. Prototipos El prototipo (prototype) de un objeto es una propiedad interna a la que me referire como "[[Prototype]]" (como en Ecma-262). Los objetos javascript pueden delegar propiedades a su [[Prototype]] (y su [[Prototype]] puede hacer lo mismo; y así hasta Object Prototype). Búsqueda de propiedades ¿Qué está pasando? Bastante simple. Notas al pie
Object Oriented Programming in JavaScript
Introduction The first version of this paper, written in 2003, had several shortcomings, not the least of which was that the techniques described were specific to Internet Explorer. I've updated and improved on the original, to document the current state of the art, especially in light of the extensive interest in AJAX technology and the increasing adoption of the FireFox browser. All the examples presented here will follow the ECMA language standards and can be applied to Internet Explorer, FireFox, and ActionScript (in Macromedia Flash). While early adopters of JavaScript used it as a simple scripting engine to create dynamic web pages, modern web designers have come to use more sophisticated object oriented techniques in building their code. I will present here, both the common paradigms used in object oriented JavaScript programming, and also suggest some helper functions that you can use in your code to streamline the process. Object Oriented Programming Goals Simple Objects References
