just-the-docs/_includes/nav.html

{%- comment -%}
  Pages with no `title` are implicitly excluded from the navigation.
  
  The values of `title` and `nav_order` can be numbers or strings.
  Jekyll gives build failures when sorting on mixtures of different types,
  so numbers and strings need to be sorted separately.

  Here, numbers are sorted by their values, and come before all strings.
  An omitted `nav_order` value is equivalent to the page's `title` value
  (except that a numerical `title` value is treated as a string).

  The case-sensitivity of string sorting is determined by `site.nav_sort`.
{%- endcomment -%}

{%- assign titled_pages = include.pages
      | where_exp: "item", "item.title != nil" -%}

{%- assign string_ordered_pages = titled_pages
      | where_exp: "item", "item.nav_order == nil" -%}
{%- assign nav_ordered_pages = titled_pages
      | where_exp: "item", "item.nav_order != nil" -%}

{%- comment -%}
  Add the nav-ordered pages to the number-ordered pages or the string-ordered pages,
  depending on their `nav_order` value.
  
  The first character of the `jsonify` result is `"` only for strings.
{%- endcomment -%}

{%- assign nav_ordered_groups = nav_ordered_pages
      | group_by_exp: "item", "item.nav_order | jsonify | slice: 0" -%}

{%- assign number_ordered_pages = "" | split: "" -%}
{%- for group in nav_ordered_groups -%}
  {%- if group.name == '"' -%}
    {%- assign string_ordered_pages = string_ordered_pages | concat: group.items -%}
  {%- else -%}
    {%- assign number_ordered_pages = number_ordered_pages | concat: group.items -%}
  {%- endif -%}
{%- endfor -%}

{%- assign sorted_number_ordered_groups = number_ordered_pages
      | sort: "nav_order" | group_by: "nav_order" -%}

{%- comment -%}
  Group the string-ordered pages by `nav_order`, if non-nil, and otherwise `title`
  (but appending the empty string to a numeric title to convert it to a string).
  
  Then sort the groups according to the site setting for case (in)sensitivity.
{%- endcomment -%}

{%- assign string_ordered_groups = string_ordered_pages
      | group_by_exp:"item", "item.nav_order | default: item.title | append: '' " -%}

{%- if site.nav_sort == 'case_insensitive' -%}
  {%- assign sorted_string_ordered_groups = string_ordered_groups
        | sort_natural: "name" -%}
{%- else -%}
  {%- assign sorted_string_ordered_groups = string_ordered_groups
        | sort:"name" -%}
{%- endif -%}

{%- assign groups_list = sorted_number_ordered_groups
      | concat: sorted_string_ordered_groups -%}

<ul class="nav-list">
  {%- for node_group in groups_list -%} 
  {%- for node in node_group.items -%}
    {%- if node.parent == nil -%}
      {%- unless node.nav_exclude -%}
      <li class="nav-list-item{% if page.collection == include.key and page.url == node.url or page.parent == node.title or page.grand_parent == node.title %} active{% endif %}">
        {%- if node.has_children -%}
          <a href="#" class="nav-list-expander" aria-label="toggle links in {{ node.title }} category">
            <svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg>
          </a>
        {%- endif -%}
        <a href="{{ node.url | relative_url }}" class="nav-list-link{% if page.url == node.url %} active{% endif %}">{{ node.title }}</a>
        {%- if node.has_children -%}
          {%- assign children_list = "" | split: "" -%}
          {%- for parent_group in groups_list -%}
            {%- assign children_list = children_list 
                  | concat: parent_group.items
                  | where: "parent", node.title
                  | where_exp:"item", "item.grand_parent == nil" -%}
          {%- endfor -%}
          {%- if node.child_nav_order == 'desc' -%}
            {%- assign children_list = children_list | reverse -%}
          {%- endif -%}
          <ul class="nav-list ">
          {%- for child in children_list -%}
            {%- unless child.nav_exclude -%}
            <li class="nav-list-item {% if page.url == child.url or page.parent == child.title %} active{% endif %}">
              {%- if child.has_children -%}
                <a href="#" class="nav-list-expander" aria-label="toggle links in {{ child.title }} category">
                  <svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg>
                </a>
              {%- endif -%}
              <a href="{{ child.url | relative_url }}" class="nav-list-link{% if page.url == child.url %} active{% endif %}">{{ child.title }}</a>
              {%- if child.has_children -%}
                {%- assign grandchildren_list = "" | split: "" -%}
                {%- for grandparent_group in groups_list -%}
                  {%- assign grandchildren_list = grandchildren_list
                        | concat: grandparent_group.items
                        | where: "parent", child.title
                        | where: "grand_parent", node.title -%}
                {%- endfor -%}
                {%- if node.child_nav_order == 'desc' -%}
                  {%- assign grandchildren_list = grandchildren_list | reverse -%}
                {%- endif -%}
                <ul class="nav-list">
                {%- for grandchild in grandchildren_list -%}
                  {%- unless grandchild.nav_exclude -%}
                  <li class="nav-list-item {% if page.url == grandchild.url %} active{% endif %}">
                    <a href="{{ grandchild.url | relative_url }}" class="nav-list-link{% if page.url == grandchild.url %} active{% endif %}">{{ grandchild.title }}</a>
                  </li>
                  {%- endunless -%}
                {%- endfor -%}
                </ul>
              {%- endif -%}
            </li>
            {%- endunless -%}
          {%- endfor -%}
          </ul>
        {%- endif -%}
      </li>
      {%- endunless -%}
    {%- endif -%}
  {%- endfor -%}
  {%- endfor -%}
  {%- assign nav_external_links = site.nav_external_links -%}
  {%- for node in nav_external_links -%}
    <li class="nav-list-item external">
      <a href="{{ node.url | absolute_url }}" class="nav-list-link external">
        {{ node.title }}
        {% unless node.hide_icon %}<svg viewBox="0 0 24 24" aria-labelledby="svg-external-link-title"><use xlink:href="#svg-external-link"></use></svg>{% endunless %}
      </a>
    </li>
  {%- endfor -%}
</ul>

{%- if page.collection == include.key -%}

  {%- for node_group in groups_list -%}
  {%- for node in node_group.items -%}
    {%- if node.parent == nil -%}
      {%- if page.grand_parent == node.title 
              or page.parent == node.title
              and page.grand_parent == nil -%}
        {%- assign first_level_url = node.url | relative_url -%}
      {%- endif -%}
      {%- if node.has_children -%}
        {%- assign children_list = "" | split: "" -%}
        {%- for parent_group in groups_list -%}
          {%- assign children_list = children_list | concat: 
                parent_group.items | where: "parent", node.title -%}
        {%- endfor -%}
        {%- if node.child_nav_order == 'desc' -%}
          {%- assign children_list = children_list | reverse -%}
        {%- endif -%}
        {%- for child in children_list -%}
          {%- if child.has_children -%}
            {%- if page.url == child.url
                    or page.parent == child.title
                    and page.grand_parent == child.parent -%}
              {%- assign second_level_url = child.url | relative_url -%}
            {%- endif -%}
          {%- endif -%}
        {%- endfor -%}
      {%- endif -%}
    {%- endif -%}
  {%- endfor -%}
  {%- endfor -%}

  {% if page.has_children == true and page.has_toc != false %}
    {%- assign toc_list = "" | split: "" -%}
    {%- for parent_group in groups_list -%}
      {%- assign toc_list = toc_list
            | concat: parent_group.items
            | where: "parent", page.title
            | where: "grand_parent", page.parent -%}
    {%- endfor -%}
    {%- if node.child_nav_order == 'desc' -%}
      {%- assign toc_list = toc_list | reverse -%}
    {%- endif -%}
  {%- endif -%}

{%- endif -%}