Aggregate hstore column in PostgreSQL 9.2 with PLV8

aggregate_hstore_with_plv8.sql

DROP FUNCTION IF EXISTS hstore_from_agg(hstores hstore[]);

CREATE FUNCTION hstore_from_agg(hstores hstore[]) RETURNS hstore AS
$$
  var result = {}

  hstores.forEach(function (sHash) {
    sHash.split(/,\s*/).forEach(function(expression) {
      var parsedValues = expression.match(/"(\d+)"=>"(\d+)"/),
          key = parsedValues[1],
          value = parseInt(parsedValues[2])
        
      if (result[key] == undefined) {
        result[key] = value
      } else {
        result[key] += value
      }
  })
})	

var resultArray = []

for (var key in result) {
  resultArray.push('"'+key+'"=>"'+result[key]+'"')
}

return resultArray.join(', ')
$$
LANGUAGE plv8 IMMUTABLE STRICT;

SELECT hstore_from_agg(array_agg(hstore_column)) from table_with_hstore
GROUP BY table_with_hstore.some_special_id;