js字符串轉數組互轉

        //字符串轉數組

        let str1="123,4,8"

        let newarr=str1.split(",")

        console.log(newarr)

        //數組轉字符串

        let result=newarr.join(",")

        console.log(result)



        //字符串截取

        console.log(str1.substring(1,3))