MediaWiki:Common.js

function attachModifiedClickHandler(element) {
    const handlers = $._data(element, 'events')?.click;
    if (handlers && handlers.length > 0) {
        const originalHandler = handlers[0].handler;

        $(element).off('click').on('click', function(event) {
            event.stopPropagation();
            originalHandler.call(this, event);
        });
        element.classList.add('FixCatTreeClick');
    }
}

addOnLoadHandler(function() {
    const observer = new MutationObserver((mutations) => {
        mutations.forEach((mutation) => {
            const target = mutation.target;

            if (
                mutation.attributeName === 'class' &&
                target.classList.contains('CategoryTreeToggleHandlerAttached') &&
                !target.classList.contains('FixCatTreeClick')
            ) {
                attachModifiedClickHandler(target);
            }
        });
    });

    observer.observe(document.body, {
        attributes: true,
        attributeFilter: ['class'],
        subtree: true
    });
});