function memory_generateConstPlayfield(
  n
) {
  var idGroups = {};
  var id = 0;
  for (let gid = 0; gid < n; ++gid) {
    idGroups[id] = gid;
    id += 1;
    idGroups[id] = gid;
    id += 1;
  }

  return idGroups;
}

function test_memory_generateConstPlayfield() {
  let idGroups = memory_generateConstPlayfield(2)
  if (
    Object.keys(idGroups).length == 4 &&
    idGroups[0] == 0 &&
    idGroups[1] == 0 &&
    idGroups[2] == 1 &&
    idGroups[3] == 1
  ) {
    return "OK: memory_generateConstPlayfield"
  }

  return "ERR: memory_generateConstPlayfield"
}

console.log(test_memory_generateConstPlayfield())