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Classical Inheritance in JavaScript

Classical Inheritance in JavaScript
Douglas Crockford www.crockford.com And you think you're so clever and classless and free — John Lennon JavaScript is a class-free, object-oriented language, and as such, it uses prototypal inheritance instead of classical inheritance. But first, why do we care about inheritance at all? The second reason is code reuse. To demonstrate this, we will introduce a little sugar which will let us write in a style that resembles a conventional classical language. Classical Inheritance First, we will make a Parenizor class that will have set and get methods for its value, and a toString method that will wrap the value in parens. function Parenizor(value) { this.setValue(value); } Parenizor.method('setValue', function (value) { this.value = value; return this; }); Parenizor.method('getValue', function () { return this.value; }); Parenizor.method('toString', function () { return '(' + this.getValue() + ')'; }); The syntax is a little unusual, but it is easy to recognize the classical pattern in it. Related:  javascript

design - How prototypal inheritance is practically different from classical inheritance Simple JavaScript Inheritance I’ve been doing a lot of work, lately, with JavaScript inheritance – namely for my work-in-progress JavaScript book – and in doing so have examined a number of different JavaScript classical-inheritance-simulating techniques. Out of all the ones that I’ve looked at I think my favorites were the implementations employed by base2 and Prototype. I wanted to go about extracting the soul of these techniques into a simple, re-usable, form that could be easily understood and didn’t have any dependencies. Additionally I wanted the result to be simple and highly usable. Here’s an example of what you can do with it: A couple things to note about this implementation: Creating a constructor had to be simple (in this case simply providing an init method does the trick).In order to create a new ‘class’ you must extend (sub-class) an existing class.All of the ‘classes’ inherit from a single ancestor: Class. Simple Class Creation and Inheritance Initialization Super Method

Building a Game with Three.js, React and WebGL — SitePoint I’m making a game titled “Charisma The Chameleon.” It’s built with Three.js, React and WebGL. This is an introduction to how these technologies work together using react-three-renderer (abbreviated R3R). Check out A Beginner’s Guide to WebGL and Getting Started with React and JSX here on SitePoint for introductions to React and WebGL. This article and the accompanying code use ES6 Syntax. How It All Began Some time ago, Pete Hunt made a joke about building a game using React in the #reactjs IRC channel: I bet we could make a first person shooter with React! I laughed. Years later, that’s exactly what I’m doing. Charisma The Chameleon is a game where you collect power-ups that make you shrink to solve an infinite fractal maze. Why React? I know what you’re thinking: why? “Declarative” views let you cleanly separate your scene rendering from your game logic.Design easy to reason about components, like <Player />, <Wall />, <Level />, etc. Recommended Courses Wes Bos React and WebGL Debugging

Private Static Members in Javascript Introduction It was a widely held belief that javascript objects could not have private instance members, that all javascript object properties where public and could be accessed and changed with external code. Douglas Crockford has demonstrated that closures can be used to provide javascript objects with private members. Douglas Crockford describes how the invocation of the constructor forms a closure that allows all of the parameters, local variables and any functions defined as function fncName(){ ... ); within the constructor to remain associated with the object that is constructed as its private members. Public and private are terms directly from class based languages (joined by "package" and "protected" in Java), privileged is a term that I think Mr Crockford coined to describe the special role of the constructor's inner functions assigned to externally accessible instance members. Javascript static members defined as properties of the constructor object are public static members.

Truth, Equality and JavaScript You don’t have to be a JavaScript novice to get confused by this… or this… The good news is that there is a standard and all browsers follow it. Some authors will tell you to fear coercion and and code against it. I hope to persuade you that coercion is a feature to be leveraged (or at the very least understood), not avoided… Is x true? Does x equal y? Conditionals In JavaScript, all conditional statements and operators follow the same coercion paradigm. The construct if ( Expression ) Statement will coerce the result of evaluating the Expression to a boolean using the abstract method ToBoolean for which the ES5 spec defines the following algorithm: Now we can see why, in the introductory example, if ([0]) allows entry to the subsequent block: an array is an object and all objects coerce to true. Here’s a few more examples. The Equals Operator (==) The == version of equality is quite liberal. Anyway, rant over, lets take a look at the way ECMA defines how == works. [0] == true; Like this:

5 Must-Reads on JavaScript Inheritance By Karthik Viswanathan Do you know inheritance in JavaScript? Do you truly understand how it works? Are you aware that JavaScript uses a prototypal inheritance scheme that is often disfavored or disliked? Have you used a script on the web to adapt this scheme to classical inheritance? In these past few days, I’ve been writing a jQuery slider plugin with various transition effects. Inheritance in JavaScript has been a controversial subject. 1. This reading isn’t really about inheritance, but it’s an important primer on object-oriented programming in JavaScript which will help give you a deeper understand of what is to come. 2. John Resig, the creator of the jQuery JavaScript library, presents his own take on inheritance. 3. Steffen Rusitschka explains the advantages and disadvantages of prototype-based and closure-based (more classical) inheritance. 4. 5. In this reading, Crockford analyzes his old classical inheritance and realizes the benefits of sticking with the prototypal structure.

OOP in JS, Part 1 : Public/Private Variables and Methods This page shows how to create private variables and methods in "classes" in Javascript through the rather simple example of a person. (This is really a very rough approximation of the classical OOP pattern, and not necessarily a "best-practice" for JavaScript programming.) Part 2 covers inheritance. Summary Example In this example, a person's name and race are set at birth and may never be changed. <- click to run the example code below (the code block being run appears after the Person constructor). The Example Code Notes This page copyright ©2003 by Gavin Kistner.

Automate Your Development Workflow With GulpJS TL;DR: In this tutorial, I'll introduce you to GulpJS and show you how to set it up in your application for task automation. GulpJS is a JavaScript task runner that lets you automate several tasks during development. These tasks involve minifying JavaScript and CSS files, automatically refreshing the browser once a file has been edited, compiling CSS preprocessors, running tests, compressing images, and several others. "GulpJS solves the problem of repetition." GulpJS is a build tool that helps you as a developer get rid of manually running such tasks as mentioned above during development for every project. GulpJS Requirements In order to use GulpJS, you need to have the following tools installed on your machine. Node.js: Navigate to the Node.js website and install the latest version on your machine.GulpJS: Install Gulp globally in your terminal so that the gulp command can be run from any directory. npm install gulp-cli -g GulpJS Features GulpJS provides a standardized API. Gulp Plugins

A JavaScript Module Pattern Eric Miraglia (@miraglia) is an engineering manager for the YUI project at Yahoo. Eric has been at Yahoo since 2003, working on projects ranging from Yahoo Sports to YUI. For the past several years, Eric and his colleagues on the YUI team have worked to establish YUI as the foundation for Yahoo’s frontend engineering work while open-sourcing the project and sharing it with the world under a liberal BSD license. Eric is an editor and frequent contributor to YUIBlog; his personal blog is at ericmiraglia.com. Global variables are evil. Douglas Crockford has been teaching a useful singleton pattern for achieving this discipline, and I thought his pattern might be of interest to those of you building on top of YUI. 1. YAHOO.namespace("myProject"); This assigns an empty object myProject as a member of YAHOO (but doesn’t overwrite myProject if it already exists). 2. 3. In the codeblock above, we’re returning from an anonymous function an object with two members. 4.

ECMAScript 5 Strict Mode, JSON, and More Previously I analyzed ECMAScript 5’s Object and Property system. This is a huge new aspect of the language and deserved its special consideration. There are a number of other new features and APIs that need attention, as well. The largest of which are Strict Mode and native JSON support. Strict Mode Strict Mode is a new feature in ECMAScript 5 that allows you to place a program, or a function, in a “strict” operating context. Since ECMAScript 5 is backwards-compatible with ECMAScript 3, all of the “features” that were in ECMAScript 3 that were “deprecated” are just disabled (or throw errors) in strict mode, instead. Strict mode helps out in a couple ways: It catches some common coding bloopers, throwing exceptions.It prevents, or throws errors, when relatively “unsafe” actions are taken (such as gaining access to the global object).It disables features that are confusing or poorly thought out. Most of the information about strict mode can be found in the ES5 specification [PDF] on page #235.

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