Javascript: 선언적 vs 명령적 프로그래밍 스타일

명령형 스타일:

const employees = [
{id: 1, name: 'james', dept: 'admin', salary: 10000},
{id: 1, name: 'Tom', dept: 'finance', salary: 10000},
{id: 1, name: 'peter', dept: 'justCode', salary: 12500},
{id: 1, name: 'tunner', dept: 'justCode', salary: 14500},
];

const justCodeDept = [];

// filter employees based on dept name.
for (let i=0; i<employees.length; i++) {
  if (employees[i].dept === 'justCode') {
    justCodeDept.push(employees[i]);
  }
}

// summation of justCodeDept employees.
let summation = 0;
for (j = 0; j<justCodeDept.length; j++) {
  summation = summation + justCodeDept[j].salary;
}

console.log(summation);

선언적 스타일:

const employees = [
{id: 1, name: 'james', dept: 'admin', salary: 10000},
{id: 1, name: 'Tom', dept: 'finance', salary: 10000},
{id: 1, name: 'peter', dept: 'justCode', salary: 12500},
{id: 1, name: 'tunner', dept: 'justCode', salary: 14500},
];

console.log(employees.filter(item => item.dept === 'justCode').reduce(((previousValue, currentValue) => previousValue += currentValue.salary), 0));