Trying to change properties in copied javascript array

Question

Im trying to get a function put together on a project. I have an array being generated by a function that is made up of objects. The first layer of the array is company, and then inside each company are the users.

First and foremost, I need to parse through all the users and change any instance of the FirstName or LastName where undefined to be an empty string.

I have done this successfully, but the issue is that my code seems to be impacting both the original array (which I do not want to touch at all), and my copy. When I run this code, the undefined names are changed to empty strings in both.

I have tried every way imaginable to copy the array and it does not seem to matter which method I use. JSON.Stringify almost looked like it would work, but it completely eliminiated all undefined properties from the source array, which is a no go.

The issue remains, so I suspect the issue is with my code for the replacement itself, shown below.

const companies = createAll();
const copyCompanies = companies.slice();

const changeUndefined = (companiesAtt) => {
  const usersArr = companiesAtt.map((company) => {
    return company.users.map((eachUser) => {
      for (let property in eachUser) {
        if (eachUser[property] === undefined) {
          eachUser[property] = '';
        }
      }
      return eachUser;
    });
  });
  return usersArr;
};
cleanConsole(1, companies);

console.log(
  '----SOLUTION EXAMPLE 1 --- ',
  changeUndefined(copyCompanies)
);

The source data and functions are below:

const firstName = [
  'joe',
  'jane',
  'seb',
  'alina',
  'fabien',
  'merwan',
  'anna',
  'annah',
  'Fathma',
  'Mohamed',
  'Walid',
  'Josiane',
  undefined,
];
const lastName = [
  'Dupont',
  'Dupond',
  'Durand',
  'Kassir',
  'Dalachra',
  'Hussein',
  'Wartani',
  'Thoumsi',
  'Angello',
  undefined,
];

const companyNames = [
  'apple',
  'microsoft',
  'Louis-vuitton',
  'Nike',
  'Channel',
  'Dior',
  'Slack',
  'Uber',
];

function createRandomNumber(min, max) {
  return Math.floor(min + Math.random() * (max - min));
}

function getValue(array) {
  return array[createRandomNumber(0, array.length + 2)];
}

function createCompany(name, index) {
  const users = createUser(createRandomNumber(10, 50));
  return {
    name,
    users,
    isOpen: !!createRandomNumber(0, 2),
    usersLength: users.length,
    id: index,
  };
}

function createUser(end) {
  const tab = [];

  for (let i = 0; i < end; i++) {
    tab.push({
      firstName: getValue(firstName),
      lastName: getValue(lastName),
      age: createRandomNumber(10, 120),
      car: !!createRandomNumber(0, 2),
      id: tab.length,
    });
  }
  return tab;
}

let companies;

export function createAll() {
  if (!companies) {
    companies = companyNames.map(createCompany);
  }
  return companies;
}

export function clone(value) {
  return Object.keys(value).map((key) => {
    value[key].users = value[key].users.map((user) => ({ ...user }));
    value[key] = { ...value[key] };
    return value[key];
  });
}

export function cleanConsole(index, value) {
  const result = clone(value);
  console.log(
    `---- EXAMPLE ${index} --- values before your modifications  :`,
    result
  );
}

Any ideas would be greatly appreciated. I feel like I am missing something important.