11.1 ECMAScript in VoiceXML

A compliant VoiceXML browser must fully implement the scripting language variously known as JScript, JavaScript or ECMAScript. Officially, the language is defined by the ECMA-262 standard produced by the ECMA standards organization (www.ecma.ch) and adopted in June 1997. It is essentially identical to the ISO/IEC 16262 standard (www.iso.ch) which was based on ECMA-262 and approved in April 1998.

The language was invented by Brendan Eich of Netscape and was first supported by Netscape's Navigator 2.0 browser and later by Microsoft in Internet Explorer 3.0. All subsequent browsers from both companies have supported JavaScript (Netscape's name) or JScript (Microsoft's name), though with some significant version and dialect differences.

ECMAScript (as we shall call it here) is a powerful and quite complex language. It is beyond the scope of this book to give a complete tutorial or reference, however there are many books, Web sites and other resources available for the reader who needs a more elementary introduction or wishes to gain a more complete understanding. Our goal here will be to provide a solid understanding of the language sufficient for a typical VoiceXML developer. We assume that the reader is familiar with programming language concepts and preferably has some knowledge of C, C++ or Java.

Adding ECMAScript to VoiceXML allows the application to make sophisticated decisions and manipulate data on the client, for example to validate user input, without having to involve the server. There are no functions which allow access to external APIs such as the...