Variations of the language attribute
The variation of the language attribute occurs in the
version number. You see, in the beginning of time, the only valid "language"
value was "JavaScript." Then as JavaScript grew to support more features,
the language attribute was used to indicate to the browser the version of
JavaScript the containing script relies on, giving the browser the choice
whether to execute the script or not depending on whether the browser
supported these features. Here's an example of a language attribute
declaration with version notes:
<script language="JavaScript1.5">
alert("hi!")
</script>
As of IE6, up to "JavaScript1.3" is supported, while in
Firefox 1.x, "JavaScript1.5." So if you think about it, the above script
will NOT be run in IE6, as IE6 will see such a language attribute as meaning
it is incapable of running the containing script.
Here's an easy way to see up to what version of JavaScript
your browser supposedly supports:
<script language="javascript">
var js_version =1.0
</script>
<script language="javascript1.1">
js_version=1.1
</script>
<script language="javascript1.2">
js_version=1.2
</script>
<script language="javascript1.3">
js_version=1.3
</script>
<script language="javascript1.4">
js_version=1.4
</script>
<script language="javascript1.5">
js_version=1.5
</script>
<script language="javascript2.0">
js_version=2.0
</script>
<script language="javascript">
document.write('<b>Your browser supports JavaScript ' + js_version + '</b>')
</script>
Output:
Now, as mentioned, the language attribute is optional,
though it serve sas an easy way to write JavaScript version specific code in
the rare cases demanding it. Browsers that do not support the JavaScript
version indicated by the language attribute do not even load the script into
memory for sake of efficiency.
Moving on, I'll demonstrate just how to use the language
attribute to your advantage when writing scripts.
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