arrays - 固定长度的元组

Question

元组中的 Typescript 允许添加以前使用过的任何类型的额外元素，但我想限制长度。我试过 & { length: 2 } , but it didn't helped :

declare var a: [string, number] & { length: 2 };

a[0] = "1"
a[1] = 2;
a[2] = "3";
a[3] = 4;

[2] 和 [3] 的赋值不会产生错误。如何指定对应的类型？

Answer 1

使用类型 never for array tail :

declare var a: [string, number, ...never[]];

你会得到

Type '"3"' is not assignable to type 'never'.

Type '4' is not assignable to type 'never'.