starting of a postgresql jsonb aggregate function to merge documents together

aggregate_function.sql

create or replace function jsonb_or(state jsonb[], current_val jsonb) returns jsonb[] as $$

    if (!state) {
        state = [];
    }

    state.push(current_val);

    return state;

$$ language plv8;

create or replace function jsonb_or_final(state jsonb[]) returns int as $$
    -- todo or the docs together...
    return state.length;
$$ language plv8;

create aggregate jsonb_or_agg(jsonb)
(
    sfunc = jsonb_or,
    stype = jsonb[],
    finalfunc = jsonb_or_final
);

select jsonb_or_agg(data) from test_actions group by action_set;