2.3 JavaScript and ECMA 262
JavaScript was first introduced in Netscape 3.0 as a client side language that had a primary function of allowing designers to validate information in a web from before it got sent to the server. This was when a majority of internet users were connecting on 28.2 kbs dialup modems and to reload a webpage could take minutes instead of seconds (Zakas, 2005). Microsoft produced a similar language called JScript to compete with JavaScript to be used in Internet explorer. Early versions of JavaScript and JScript had different syntax although very similar. Eventually the different languages were standardised.
“In 1997, JavaScript 1.1 was submitted to the European Computer Manufacturers Association (ECMA) as a proposal.” (Zakas, 2005). Technical Committee #39 (TC39) was set up “To standardize: the syntax and semantics of the general purpose, cross platform, vendor-neutral scripting language ECMAScript; ECMAScript for XML.” (ECMA, 2008). This created standard ECMA 262.
ECMA 262 is a language specification that JScript 5.6 (MSDN, 2008) and JavaScript 1.5 (Mozzilla Developer Center, 2008) both fully implement. I will refer to the implementation of ECMA in both JScript and JavaScript as the term JavaScript, highlighting the differences for browsers. It is important to understand the differences between JScript and JavaScript when building any JavaScript rich application including AJAX enabled websites. If you do not cater for the difference in web browser then you automatically exclude people from your site decreasing its accessibility.
It is commonly thought that all JavaScript is inaccessible. However Kirkpatrick argues that “Screen readers have improved support for JavaScript in recent versions. There are more and more events that will trigger updates to the page models and data structures on which screen readers rely. As a result, more and more JavaScript-created content is accessible to screen readers, at least in theory.” (Thatcher et al, 2006). There are still compatibility problems with the screen readers and JavaScript. There are a lot of users who will have JavaScript disabled for a number of reasons. If the JavaScript used on one’s site conveys important information to a user then a non-scripting alternative must be used.