Company

class Company {
  constructor() {
    this.departments = [];
  }

  addEmployee(...params) {
    let [name, salary, position, department] = params;
    let departmentPresent = false;

    // invalid input test
    const test = (ele) => ele === undefined || ele === null || ele === '';
    let isInvalidInput = params.some(test) || salary < 0;

    if (isInvalidInput) {
      throw new Error('Invalid input!');
    }

    // create new employee
    const empObj = {
      name,
      salary,
      position,
      department,
    };

    // check if department exists
    this.departments.forEach((depObj) => {
      if (depObj.name === department) {
        departmentPresent = true;

        // if department is already present
        // add the new employee to it
        depObj.employees.push(empObj);
        return;
      }
    });

    // if department doesn't exist, add the new one
    if (!departmentPresent) {
      // create new department object
      const departmentObj = {
        name: department,
        // the new employee is the first one in this department
        // so it's the only one in the employees array
        employees: [empObj],
        totalSalary: function () {
          return (
            this.employees.reduce((acc, cur) => {
              return acc + Number(cur.salary);
            }, 0) / this.employees.length
          );
        },
      };

      this.departments.push(departmentObj);
    }

    return `New employee is hired. Name: ${name}. Position: ${position}`;
  }

  bestDepartment() {
    let output = [];
    let name = '';

    // extract the department with the highest salary out
    let bestSalary = this.departments.reduce(
      (highestSalary, currentDepartment) => {
        let currHigh = currentDepartment.totalSalary();

        if (currHigh > highestSalary) {
          // save best department's name and avg salary
          name = currentDepartment.name;
          return currHigh;
        }

        return highestSalary;
      },
      Number.MIN_SAFE_INTEGER
    );

    let nameLine = `Best department is: ${name}`;
    let salaryLine = `Average salary: ${bestSalary.toFixed(2)}`;
    let employeesArr = [];

    this.departments.forEach((department) => {
      if (department.name === name) {
        // find the array containing the best department's employees
        employeesArr = department.employees.map((e) => e);
      }
    });

    // sort by highest salary descending
    // sort by name
    employeesArr.sort((eA, eB) => {
      return eB.salary - eA.salary || eA.name.localeCompare(eB.name);
    });

    // add to output arr
    output.push(nameLine);
    output.push(salaryLine);
    output = output.concat(
      employeesArr.map((e) => `${e.name} ${e.salary} ${e.position}`)
    );

    return output.join('\n').trim();
  }
}