XML , XSL and JavaScript

i have one xml and xsl and i am using javascript in xsl to load xml values like

 <script type="text/javascript">
chars = "<xsl:value-of select="//system-params/login/forbiddenChars" disable-output-escaping="yes" />;
Length = <xsl:value-of select="//system-params/login/Digits" disable-output-escaping="yes" />;
</script>

and now i do not want to write above javaScript code in XSL and only want to include javascript by creating seperate file for javascript.

provide answers with exapmle by defining three (3) seperate file. i am begineer in this language.