# 15 TypeScript 高级类型

> 本文为个人学习摘要笔记。\
> 原文地址：[TypeScript 高级类型及用法](https://juejin.cn/post/6985296521495314445)

## 交叉类型 &

交叉类型是将多个类型合并为一个类型。这让我们可以把现有的多种类型叠加到一起成为一种类型，它包含了所需的所有类型的特性。

语法： `T & U`，其返回类型既要符合 `T` 类型也要符合 `U` 类型。

```typescript
interface Ant {
  name: string
  weight: number
}

interface Fly {
  flyHeight: number
  speed: number
}

// 少了任何一个属性都会报错
const flyAnt: Ant & Fly = {
  name: '蚂蚁呀嘿',
  weight: 0.2,
  flyHeight: 20,
  speed: 1,
}
```

## 联合类型 |

联合类型将多个类型组合成一个类型，可以是多个类型的任意一个。

语法：`T | U`，其返回类型为连接的多个类型中的任意一个。

```typescript
class Bird {
  fly() {
    console.log('Bird flying')
  }
  layEggs() {
    console.log('Bird layEggs')
  }
}

class Fish {
  swim() {
    console.log('Fish swimming')
  }
  layEggs() {
    console.log('Fish layEggs')
  }
}

const bird = new Bird()
const fish = new Fish()

function start(pet: Bird | Fish) {
  // 调用 layEggs 没问题，因为 Bird 或者 Fish 都有 layEggs 方法
  pet.layEggs()

  // 会报错：Property 'fly' does not exist on type 'Bird | Fish'
  // pet.fly();

  // 会报错：Property 'swim' does not exist on type 'Bird | Fish'
  // pet.swim();
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://chanshiyu.gitbook.io/blog/qian-duan/javascript/15typescript-gao-ji-lei-xing.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.