_includes/language-switch.html

{% if page.collection == "docs" %}
{% assign lang_switch_button = "is-light is-outlined is-inverted" %}
{% else %}
{% assign lang_switch_button = "is-primary is-outlined is-inverted" %}
{% endif %}

<!--A simple language switch button that only supports zh and en.-->
<!--IF its language is zh, then switches to en.-->
{% if site.active_lang == "zh" %}
<a class="button {{ lang_switch_button }}" href="{{ page.url | prepend: '/en' }}"><strong>En</strong></a>
{% elsif site.active_lang == "en" %}
<!--If you don't want a url to be relativized, you can add a space explicitly into the href to 
    prevents a url from being relativized by polyglot.-->
<a class="button {{ lang_switch_button }}" href=" {{ page.url }}"><strong>中</strong></a>
{% endif %}