Sams Teach Yourself JavaScript in 24 Hours

Specifying JavaScript Versions

As mentioned earlier in this hour, you can specify a version of JavaScript in the <script> tag. For example, this tag specifies JavaScript version 1.3:

<script language="JavaScript1.3" type="text/javascript">

There are two ways of specifying the JavaScript language in the <script> tag. The old method uses the language attribute, and the new method recommended by the HTML 4.0 specification uses the type attribute. To maintain compatibility with older browsers, you can use both attributes.

When you specify a version number in the language attribute, this allows your script to execute only if the browser supports the version you specified or a later version.

When the <script> tag doesn't specify a version number, all browsers that support JavaScript will run the script. Because most of the JavaScript language has remained the same since version 1.0, you will rarely need to worry about JavaScript versions.