Creates an object with keys from an array and its translated values, then outputs it as a json string

array-to-object.twig

{% set labels = ['welcome', 'ok', 'cancel'] %}
{% set obj = labels|reduce((carry, key) => carry|merge({ (key): key|t|ucfirst }), {}) %}
{{ obj|json_encode }}

{# as a macro #}
{% macro translateToJSON(labels) %}{% spaceless %}
{{ labels|reduce((carry, key) => carry|merge({ (key): key|t|ucfirst }), {})|json_encode }}
{% endspaceless %}{% endmacro %}