TS學習之for..of

for..of會遍歷可迭代的對象，調用對象上的Symbol.iterator方法（可迭代對象，數組，字符串等）

let arr = ["hello", "ts", "test"];
for (let item of arr) {
    console.log(item)
}
//"hello", "ts", "test"

for...of VS for...in（均可迭代一個列表。但是用於迭代的值卻不同，for..in迭代的是對象的 鍵 的列表，而for..of則迭代對象的鍵對應的值。）

let list = [4, 5, 6];

for (let i in list) {
    console.log(i); // "0", "1", "2",
}

for (let i of list) {
    console.log(i); // "4", "5", "6"
}

let pets = {1:"Cat",2:"Dog",3:"Hamster"}
for (let pet in pets) {
    console.log(pet); // 1,2,3
}
for (let pet of pets) {
    console.log(pet); // "Cat", "Dog", "Hamster"
}