typescript类型问题

Question

const a = [1, '2', {}, {a: 1}, null];
根据上述代码语句怎么推断出下面ts类型。

[1, '2', {}, {a: 1}, null] => number | string | {} | {a : 1}

Answer 1

const d = [1, '2', {}, {a: 1}, null] as const;

type RmReadonly<T extends object> = {
    -readonly [key in keyof T]: T[key];
}

type GetType<D> = {
    [key in keyof D]: D[key] extends null ? never :  D[key] extends object ? RmReadonly<D[key]> : D[key];
}

type Result = GetType<typeof d>[number]

这样试试

Answer 2

参考一下

const a = [1, '2', {}, {a: 1}, null] as const;

type Result = (typeof a) extends readonly (infer T)[]? NonNullable<T>:never

// 结果是： 1 | "2" | {} | {readonly a: 1;}

新手上路，回答的第一个问题，给个赞吧

Answer 3

const a = [1, '2', {}, {a: 1}, null];

type A = typeof a[0];