CDATA required for javascript????

I noticed that several books put javascript in CDATA,
but also found that javascript also worked without
CDATA.  
<script language="javascript">
    document.write(form.first_elem.value);
</script>

or

<script language="javascript">
    <xsl:comment>
        <![CDATA[
            document.write(form.first_elem.value);
        ]]>
    </xsl:comment>
</script>

Both of the above works fine.

I wonder if it is just a matter of style, or it
requires CDATA in some special cases.

Thanks.

Yan


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