javascript

The Evolution of
JavaScript
With the renewed interest in web development since 2004, conversations began taking place
among browser vendors and other interested parties as to how JavaScript should evolve. Work on
the fourth edition of ECMA - 262 began based largely on two competing proposals: one for
Netscape ’ s JavaScript 2.0 and the other for Microsoft ’ s JScript.NET. Instead of competing in the
browser realm, the parties converged back into ECMA to hammer out a proposal for a new
language based on JavaScript. Initially, work began on a proposal called ECMAScript 4, and for a
long time, this seemed like the next evolutionary step for JavaScript. When a counterproposal
called ECMAScript 3.1 was later introduced, it threw the future of JavaScript into question. After
much debate, it was determined that ECMAScript 3.1 would be the next step for JavaScript and
that a further effort, code-named Harmony, would seek to reconcile some features from
ECMAScript 4 into ECMAScript 3.1. To understand how this will affect JavaScript in the future, it ’ s
important to take a look at all of the steps along this process.
ECMA Script 4/JavaScript 2
The ECMAScript 4 proposal was originally scheduled to be completed by October 2008 and is still
in flux at the time of this writing. There are several parts of the language that are likely to be in the
final version and deserve some attention. Mozilla had taken an approach of implementing small
sets of proposed ECMAScript 4 functionality through a series of JavaScript releases beginning with
JavaScript 1.5 in Firefox 1 and culminating with JavaScript 2 in Firefox 4.
There are a series of changes being actively made to JavaScript and a series of proposed changes
being made to ECMAScript through specification changes. The changes are grouped accordingly
in the following material to give you some idea as to what is already available and what may be
coming. All of the changes made in JavaScript 1.5 through 1.9 are part of the ECMAScript 4
proposal.