JavaScript how to handle Node callbacks correctly, code running out of order when importing functions

Question

I'm new to JS and Node, i've been trying to write an API for people management like keeping track of employees absences and I'm using Node with express.js.

I currently ran into a problem of ordering when i decided to put the functions in their own module/file.

I basically want to retrieve a employee absences when a manager does a GET request on localhost:3000/user/$userId , but my functions are running out of order and i've been reading about node callbacks but i still couldn't figure it out.

Code of the API call:

/* Returns for each employee find her/his absences */
app.get('/user/:userId', async (req, res) => {
  let employee = api.getEmployeeAbsences(req.params.userId);
  console.log(`Employee retrivied ${employee}`);
});

Code of the API function that retrives the employee and his absences.

const readJsonFile = (path) => new Promise((resolve) => fs.readFile(path, 'utf8', (_, data) => resolve(data)))
  .then((data) => JSON.parse(data))
  .then((data) => data.payload);

export const members = () => readJsonFile(MEMBERS_PATH);
export const absences = () => readJsonFile(ABSENCES_PATH);

var exports = module.exports = {};

/* Returns the employee(given by the userId) info and his last absence if she or he exists */
exports.getEmployeeAbsences = function(userId) {
  console.log('Start of Function');
  members().then((employees) => {
    console.log('Members');  
    let employee = employees.filter(emp => userId == emp.userId)[0];
    // If employee wasn't found
    if (!employee) {
      return undefined;
    } else {
      absences().then((absences) => {
        console.log('Absences');
        // Assigning employee absences
        employee = Object.assign(employee, { absences: absences.filter(abs => employee.userId == abs.userId) });
        console.log(employee);
        return employee;
      });
    }
  });
  console.log(`End of function ${userId}`);
}

Out of Order Output Example: