---
title: 类型体操
author: powerfulyang
public: true
date: 2023-01-04
summary: 非空数组的类型，元素非空数组的类型
tags: 
    - typescript
    - type-challenges
    - non-empty array
    - non nullable element array
---

## How to type a non-empty array in typescript?
```typescript
export type NonEmptyArray<T> = [T, ...T[]];
```

## How to type a array which shouldn't contain nullable item?
```typescript
export type NonNullableElement<T> = T extends (infer U)[] ? NonNullable<U>[] : T;
```

类型体操

非空数组的类型，元素非空数组的类型