Drupal - How to display a comma-separated list of multiple field values?

While it's possible to use CSS for this I think it's better to avoid it. I've simplified the field twig file to illustrate, but it would look something like this:

{% for item in items %}
  {% if loop.last %}
    {% set separator = '' %}
  {% else %}
    {% set separator = '/' %}
  {% endif %}
  {{ item.content }}{{ separator }}
{% endfor %}