雖然不熟悉Typescript,為了回答您的問題查詢一下文件，大體是這樣的直接上程式碼

如果陣列中元素的資料型別相同,可以簡單做。

二維 number

let arr2_num:number[][]=[[1,2,3],[4,5,6]];

console.log(arr2_num[1][0]);

//二維 string

let arr2_str:string[][]=[["0-0","0-1","0-2"],["1-0","1-1","1-2"]];

console.log(arr2_str[1][1]);

//復聯合型別和介面方式實現巢狀陣列 interface DeepArray<T> extends Array<T | DeepArray<T>> {}

const array: DeepArray<string | boolean> = [ "str_0", true, ["str_2_0"], [true, ["str_3_0","str_3_1"]], [[["str----", false, "str....."]]],];

console.log(array[0],array[3][1][1]);