first

The first filter returns the first "element" of a sequence, a mapping, or a string:

{{ [1, 2, 3, 4]|first }}
{# outputs 1 #}

{{ { a: 1, b: 2, c: 3, d: 4 }|first }}
{# outputs 1 #}

{{ '1234'|first }}
{# outputs 1 #}