trello.com.html

    function appendLists(el) {
        const boardId = el.value

        // skip boards with no lists
        if (!lists[boardId]) { return }

        // create a new ul
        let ul = document.createElement('ul')

        // append all the list li's to the new ul
        lists[boardId].forEach(li => ul.appendChild(li))

        // append the new ul to the boards li
        el.closest('li').appendChild(ul)
    }