Alphabetical index for a list of entries

Question

I would like to build an alphabetical list of craft entries, but group them by the initials of one field of each entry. Thus, getting some kind of alphabetical index, like

A

• Apples
• Ananas

B

• Beer

How do I do that?

Answer 1

First, sort all entries by multiple criteria:

{# get our entries and order by firstname, lastname #}
{% set allEntries = craft.entries.section('entries').orderBy('lastname asc, firstname asc').all() %}

Then use craft's custom "group" filter (lastname[:1] picks the first letter):

{# group them by the first letter of the last name https://docs.craftcms.com/v3/dev/filters.html#group #}
{% set allEntriesByGroup = allEntries | group('lastname[:1]') %}

Then loop through that multidimensional array (firstletter, entriesInGroup) is key -> value in twig:

{% for firstletter, entriesInGroup in allEntriesByGroup %}
    <h3>{{firstletter}}</h3>
    <ul>
    {% for entry in entriesInGroup %}
       <li>{{entry.lastname}}, {{entry.firstname}}</li>
    {% endfor %}
    </ul>
{% endfor %}