https://medium.com/p/c19c023fc755/edit part 2

udf.js

function intdiv(row, emit) {
    emit({ d: row.x / row.y, m: row.x % row.y });
}
bigquery.defineFunction(
    'intdiv',
    ['x', 'y'],
    [{ 'name': 'd', 'type': 'integer' },
    { 'name': 'm', 'type': 'integer' }],
    intdiv
);

udf.sql

SELECT d, m FROM intdiv(
  SELECT 21 as x, 4 as y
);