for of, for in 구문

for …of 반복문

var iterable = [10, 20, 30];
for (var value of iterable) {
  console.log(value); // 10, 20, 30
}
for (var value of 'basket') {
  console.log(value); // b a s k e t
}

for …in 반복문

var iterable = [10, 20, 30];
var obj = {
    a: 1, 
    b: 2, 
    c: 3
};
 
for (var prop in obj) {
    console.log(prop, obj[prop]); // a 1, b 2, c 3
}
for (var index in iterable) {
    console.log(index, iterable[index]); // 0 10, 1 20, 2 30
}