#utils.js
function modifyUserFieldData (userId, field, optional, data) {
  if (!exists(userId) || !exists(field) || !exists(data)) {
    return promise.reject({code: 404, msg: 'missing'})
    // return callback({code: 404, msg: 'userId, field or data missing', errorCode: errorCodes.expectedContentNotProvided})
  }
  switch (field) {
    case 'skill':
      modifyUserSmallFunc(userId, 'skills', ['id', 'userId', 'skill', 'level', 'visible'], data)
      .then(id => {
        console.log('modifyUserSmallFunc id: ', id)
        return promise.resolve(id)
      })
      .catch(err => {
        console.log('modifyUserSmallFunc err: ', err)
        promise.reject(err)
      })

      break
...