function EmployeeDetails() {
  var name: "Mayank";
  var age = 30;
  var designation = "Developer",
  var salary = 10000;

  var calculateBonus = function(amount) {
    salary = salary + amount;
  }

  return {
    name: name,
    age: age,
    designation: designation,
    calculateBonus: calculateBonus
  }
}

var newEmployee = EmployeeDetails()

var userName = newEmployee.calculateBonus(1000);