let arr = ["a","b","c"]在某些隱含轉換的應用場景或調用arr.toString()方法，arr會默認轉換成字符串a,b,c如何轉化成字符串 ["a","b","c"] ，除了自己寫處理邏輯function toNormalString(){  let str;  return str = '[' + this.join(",")+']'}Array.prototype.toNormalString = toNormalStringarr.toNormalString()除此之外，原生的數組有沒有支持類似的方法？上面這種寫法也有缺點，轉化出來的字符串是"[a,b,c]" 而不是 ["a","b","c"]