MediaWiki:Common.js

/* Any JavaScript here will be loaded for all users on every page load. */
function AppendCategoryTreeToSidebar() {
   console.log("AppendCategoryTreeToSidebar");
}
 
addOnloadHook( AppendCategoryTreeToSidebar );

mw.hook( 'wikipage.categories' ).add( function ( $content ) {
   console.log("wikipage.categories:" + $content.find( '.CategoryTreeToggle' ).length);
});