webpack-plugin/example/views/helpers/meta.njk

{# handle meta in templates #}

{% macro meta(page, site) %}
    {% if (page.meta) %}

        {% set hasCannocial = false %}

        {% for key, content in page.meta %}
            <meta name="{{ key }}" content="{{ content }}" />

            {# check for index in robots if set page has canonical #}
            {% if (key === 'robots' and content.indexOf('index') !== -1 and content.indexOf('noindex') === -1) %}
                {% set hasCannocial = true %}
            {% endif %}
        {% endfor %}

        {# check if page has canonical #}
        {% if (hasCannocial) %}
            {% set http = 'http' %}

            {% if (site.https) %}
                {% set http = site.https %}
            {% endif %}

            <link href="{{ http }}://{{ site.domain }}{{ page.path }}" rel="canonical">
            <link rel="alternate" href="{{ http }}://{{ site.domain }}{{ page.path }}" hreflang="{{ site.language }}">
        {% endif %}
    {% endif %}
{% endmacro %}