departments.js

let company = { // the same object, compressed for brevity

sales: [{name: 'John', salary: 1000}, {name: 'Alice', salary: 1600 }],

development: {

sites: [{name: 'Peter', salary: 2000}, {name: 'Alex', salary: 1800 }],

internals: [{name: 'Jack', salary: 1300}]

}

};

// The function to do the job

  function sumSalaries(department) {

    if (Array.isArray(department)) { // case (1)

      return department.reduce((prev, current) => prev + current.salary, 0); // sum the array

    } else { // case (2)

      let sum = 0;

      for (let subdep of Object.values(department)) {

      sum += sumSalaries(subdep); // recursively call for subdepartments, sum the results

    }

  return sum;

  }

  }