Here’s a a quick and easy snippet to add alternating class names to your views rows, also referred to as ‘zebra’ tables or ‘striped backgrounds’.
1. Copy
/core/modules/views/templates/views-view-unformatted.html.twig
to
/themes/custom/yourtheme/templates/views-view-unformattted--yourviewname.html.twig
2. Replace yourviewname with your view’s machine name.
3. Change the following:
{% set row_classes = [ default_row_class ? 'views-row', ] %}
to
{% set row_classes = [ default_row_class ? 'views-row', cycle(['even', 'odd'], loop.index0), ] %}
Explanation
cycle()
A core twig function that cycles through a given array of values.
loop.index0
Indicates the position (index) of the iterator during the looping, starting at 0.
More info on twig functions: https://twig.sensiolabs.org/doc/2.x/functions/index.html