JavaScript is one of the foundations of the internet as we currently know it, but is often misunderstood. It is the “J” in AJAX (to be discussed elsewhere), and is typically used for creation of interactive browser applications with client-side (browser) functionalities such as FORM validation and manipulation of onscreen elements via the DOM (to be discussed elsewhere).
JavaScript is more appropriately called ECMAScript, as it is a ‘Standard’ from the ECMA organization. Early incarnations of this specification were called LiveScript (by Netscape). Microsoft, in typical form, created a VisualBASIC like version that they called JScript, though while mostly compatible, has some proprietary differences.
Implementation:
It’s always preferred to add this to your HEAD section (or the equivalent in HTTP Headers):
<meta http-equiv=”Content-Script-Type” content=”text/javascript” />
To include external files containing JavaScript:
<script type=”text/javascript” src=”/filename.js”></script>
To include XHTML compliant blocks of JavaScript in your page:
<script type=”text/javascript”>
<!– <![CDATA[
…
//]]> — >
</script>
DO NOT use the deprecated ‘language’ attribute:
<script language=”JavaScript”>
…
</script>