This is a little XSLT snippet, that, for a given authority control id, creates a link to a corresponding wikipedia entry in a specified language

authority-wikipedia.xsl

<xsl:variable name="authority">
    <!-- here goes the authority -->
</xsl:variable><xsl:variable name="identifier">
    <!-- here goes the id -->
</xsl:variable><xsl:variable name="isoLang">
    <!-- here goes the ISO 639-1 language code -->
</xsl:variable><xsl:variable name="property">
    <xsl:choose>
        <xsl:when test="$authority = 'viaf'">
            <xsl:value-of select="214" />
        </xsl:when>
        <xsl:when test="$authority = 'gnd'">
            <xsl:value-of select="227" />
        </xsl:when>
        <xsl:when test="$authority = 'lcnaf'">
            <xsl:value-of select="244" />
        </xsl:when>
    </xsl:choose>
</xsl:variable>
<xsl:variable name="query" select="document(concat('https://query.wikidata.org/sparql?query=SELECT%20%3Farticle%20WHERE%20%7B%0A%20%20%20%20%3Fitem%20wdt%3AP', $property,'%20%22', $identifier,'%22%20.%0A%20%20%20%20%3Farticle%20schema%3Aabout%20%3Fitem%20.%0A%20%20%20%20%3Farticle%20schema%3AinLanguage%20%22', $isoLang,'%22%20.%0A%20%20%20%20%3Farticle%20schema%3AisPartOf%20%5B%20wikibase%3AwikiGroup%20%22wikipedia%22%20%5D.%0A%7D'))" />
<xsl:variable name="link" select="$query//*[local-name() = 'uri'][1]" />
<xsl:if test="$link">
    <a class="wikilink">
        <xsl:attribute name="href">
            <xsl:value-of select="$link" />
        </xsl:attribute>
        <xsl:attribute name="target">
            <xsl:value-of select="'_blank'" />
        </xsl:attribute>
        <xsl:attribute name="title">
            <xsl:value-of select="'Wikipedia'" />
        </xsl:attribute>
        <span class="fab fa-wikipedia-w"></span>
    </a>
</xsl:if>

You could do this with JavaScript, but this little query is extremely fast, so no need to do it asynchronously.