Common.js

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// Replace Wikidata IDs with their [label, description]
$( '.wb-external-id' ).each( function() {
    if ( $( this ).attr( 'href' ).lastIndexOf( 'https://www.wikidata.org', 0 ) === 0 ) {
        var wikidataApi = new mw.ForeignApi( 'https://www.wikidata.org/w/api.php', {
                anonymous: true,
                parameters: { 'origin': '*' },
                ajax: { timeout: 10000 }
            } ),
            lang = mw.config.get( 'wgUserLanguage' ),
            node = $( this );
        wikidataApi.get( {
            'action': 'wbgetentities',
            'format': 'json',
            'ids': node.text(),
            'props': 'labels|descriptions',
            'languages': lang,
            'languagefallback': 1,
            'origin': '*'
        } ).then( function( data ) {
            var entity = data.entities[ node.text() ],
                label = entity.labels[ lang ].value,
                description = entity.descriptions[ lang ].value;
            
            node.html( '<b>' + label + '</b><br><small>' + description + '</small>' )
        } );
    }
} );