function createEl(d, container) {
        var link = container.appendChild(createLink(d))
        if (d.children.length) {
            var list = createList(d.isCollapsed)
            d.children.forEach(function (child) {
                createEl(child, list)
            })
            link.appendChild(list)
        }
    }
Create link and list elements.
@param {Object} d
@param {HTMLElement} container
@return {HTMLElement}