How to assign the class "active" based on the path /{{ site.lang }} {{ page.url }}?

[blog]

@rdyar

{% if child.url == site.lang | append: page.url %}
it works!
{% else %}
it doesn't work, child.url = {{child.url}} <br/>
page url with append: {{ site.lang | append: page.url }}
{% endif %}

This code outputs:

it doesn't work, child.url =
page url with append: en/articles/cryptocurrency/