MediaWiki:Common.js

$(function () {
    var toc = document.getElementById('toc');
    var tools = document.getElementById('p-tb');
    var admin = document.getElementById('p-managewiki-sidebar-header');

    if (toc && tools) {
        var tocClone = toc.cloneNode(true);
        tocClone.id = 'toc-sidebar';
        tocClone.style.display = 'block';

        var wrapper = document.createElement('nav');
        wrapper.className = 'mw-portlet';
        wrapper.setAttribute('aria-labelledby', 'p-toc-label');
        wrapper.innerHTML = `
            <h3 id="p-toc-label" class="vector-menu-heading">Contents</h3>
            <div class="vector-menu-content">
                <div class="vector-menu-content-list"></div>
            </div>
        `;
        wrapper.querySelector('.vector-menu-content-list').appendChild(tocClone);

        if (admin && $(admin).is(':visible')) {
            admin.parentNode.insertBefore(wrapper, admin.nextSibling);
        } else {
            tools.parentNode.insertBefore(wrapper, tools.nextSibling);
        }

        $('#toc').hide();
    }
});