javascript - TypeScript 返回不可变/常量/只读数组

Question

我想要一个返回数组的函数，但我希望返回的数组是只读的，所以当我尝试更改其内容时应该会收到警告/错误。

function getList(): readonly number[] {
   return [1,2,3];
}


const list = getList();
list[2] = 5; // This should result in a compile error, the returned list should never be changed

这可以在 TypeScript 中实现吗？

Answer 1

这似乎可行...

function getList(): ReadonlyArray<number> {
    return [1, 2, 3];
}

const list = getList();

list[0] = 3; // Index signature in type 'ReadonlyArray<number>' only permits reading.

在 Playground 中尝试

ReadonlyArray<T>是这样实现的:

interface ReadonlyArray<T> {
    readonly [n: number]: T;
    // Rest of the interface removed for brevity.
}