const number2DArr : number[][] = [
[1,2,3],
[4,5,6]
]
const str2DArr = [
['1', '2', '3'],
['4', '5', '6']
] //string[][]
str2DArr는 string[][]로 네로잉 된다.
const strAndNumberArr : (number | string)[][] = [
[1, '2', 3],
['4', 5, '6']
]
let strArrOrNumberArr: string[][] | number[][] = [
[1, 2, 3],
[4, 5, 6]
]
strArrOrNumberArr = [
['1', '2', '3']
]