<nav class=“navbar navbar-expand-lg navbar-dark bg-dark”>

{%- assign default_paths = site.pages | map: "path" -%}
{%- assign page_paths = site.header_pages | default: default_paths -%}
{%- assign titles_size = site.pages | map: 'title' | join: '' | size -%}
<div class="container">
    <a class="navbar-brand" href="{{ "/" | relative_url }}">{{ site.title | escape }}</a>
    {%- if titles_size > 0 -%}
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav"
            aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse" id="navbarNav">
        <div class="mr-auto"></div>
        <ul class="navbar-nav">
            {%- for path in page_paths -%}
                {%- assign my_page = site.pages | where: "path", path | first -%}
                {%- if my_page.title -%}
                    <li class="nav-item active">
                        <a class="nav-link" href="{{ my_page.url | relative_url }}">{{ my_page.title | escape }}</a>
                    </li>
                {%- endif -%}
            {%- endfor -%}
        </ul>
        <form class="form-inline my-2 my-lg-0" action="/search.html" method="GET">
            <input class="form-control mr-sm-2" type="search" placeholder="Search" aria-label="Search" name="q" id="q">
            <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
        </form>
    </div>
    {%- endif -%}
</div>

</nav>