함수 선언식
function getRectangleArea (width, height) { let rectangleArea = width * height return rectangleArea }
함수 표현식 (가장 먼저 변수를 선언) + 익명함수를 할당
let getRectangleArea = function (width,height) { let rectangleArea = width * height return rectangleArea }
화살표함수
const getRectangleArea = (width, height) => { let rectangleArea = width * height return rectangleArea }
같은 코드
const getRectangleArea = (width, height) => width * height