JavaScript 2.0: A Sneak Preview

As a developer and writer, part of my job is to stay informed of current trends in the web world, whether it be company mergers, online-shopping trends, or programming technologies. I'll admit that it's hard to keep up with everything that's going on in the industry these days, but one tidbit of news is making the rounds that is raising a lot of eyebrows: the drafting of the JavaScript 2.0 proposal. The new JavaScript 2.0 / EMCAScript 4.0, isn't due to be finalized until the end of the fall of 2009, but it's already garnering lots of strong reactions - both good and bad. Today, we'll be taking a look at some of the proposed specifications and you can decide for yourself whether they constitute improvements in the language or merely unnecessary standardization.

The JavaScript Story

To better understand how JavaScript standards are implemented, let's take a brief look at the language's history.

JavaScript is a dialect of the ECMAScript scripting language, which is standardized by Ecma International. The other two dialects are ActionScript (MacroMedia, Adobe) and JScript (Microsoft). JavaScript was originally developed by Brendan Eich of Netscape. It was originally called Mocha and then LiveScript, before finally being renamed to JavaScript. Sun Microsystems released Netscape Navigator 2.0 with support for JavaScript in March of 1996. Due to the widespread success of JavaScript as a client-side scripting language, Microsoft developed their own version of the language named JScript, which was included in Internet Explorer 3.0 release of August 1996. Netscape submitted JavaScript to Ecma International for standardization, in Geneva.

Ecma International is an international, membership-based, non-profit standards organization for information and communication systems. The organization was originally founded in 1961 to standardize computer systems in Europe. In the 40 odd years since its inception, Ecma has produced more than 370 Standards and 90 Technical Reports, including CD-ROM volume and file structure, C++ Language Specification, and their Open XML format. The first edition of ECMAScript (ECMA-262) was adopted by the ECMA General Assembly of June 1997. Both JavaScript and JScript aim to be compatible with ECMAScript, while providing additional features not described in the ECMA specification. Even today, the JavaScript and JScript dialects have as many differences as commonality. JavaScript was influenced by Object-Oriented languages like Java and C++, but was meant to be easier for non-programmers to work with.

Language Enhancements

More Object Oriented

Up until now, JavaScript used prototypical inheritance rather than the classical OOP kind for inheriting from parent classes. In fact, as the following code demonstrates, there currently exists no such thing as a "class" in JavaScript:

// Current JavaScript 1.x "Class" Definition function MyClass() { this.member1 = "a string"; this.member2 = 10; } var myClass = new MyClass(); // class instantiation // JavaScript 2.0 Class Definition class TrueClass { this.member1 = "a string"; this.member2 = 10; } var trueClass = new TrueClass(); // class instantiation

Functions double as object constructors along with their typical role. Prefixing a function call with new creates a new object and calls that function with its local this keyword bound to that object for that invocation. The function's prototype property determines the new object's prototype. Whatever is assigned to an object's prototype property is shared amongst all of its instances and children. Using the prototype property, it is possible to simulate many class-based features in JavaScript, albeit with some quirks! For instance, in the following code, myOtherDog attempts to override the getBreed() function of parent Dog "class". Although the myOtherDog's getBreed() function is indeed implemented, it does not hide the parent's, giving myOtherDog two breeds!

function Dog(name) { this.name = name; this.bark = function() { alert('Woof!'); }; this.displayName = function() { alert(this.name); }; }; var myDog = new Dog('Killer'); myDog.displayName(); //Killer myDog.bark(); //Woof! Dog.prototype.getBreed = function() { alert("Mutt"); }; myDog.getBreed(); //Mutt myOtherDog = new Dog('Bowzer'); // this hides getBreed() from other Dogs myOtherDog.getBreed = function() { return "Lhasa Apso"; }; alert(myOtherDog.getBreed()); //Lhaso Apso and Mutt! alert(myDog.getBreed()); //function is undefined

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