巧用TS

1.巧用注释（/** 注释内容*/）

场景：文件内、接口描述、方法描述、字段描述等等

2.巧用typeof

比如起初写法

interface Opt {

  timeout: number

}

const defaultOption: Opt = {

  timeout: 500

}

优化后：

const defaultOption = {

  timeout: 500

}

type Opt =typeof defaultOption

3.巧用联合类型(两者必选一)

interface Dinner1 {

  fish?: number,

  bear?: number,

}

type Dinner2 = {

  fish: number,} | {

  bear: number,
}

4.巧用查找类型

interface Person {

  addr: {

    city: string,

    street: string,

    num: number,

  }}

当需要使用 addr 的类型时，除了把类型提出来

interface Address {

  city: string,

  street: string,

  num: number

}

interface Person {

  addr: Address,

}

5.巧用查找类型+泛型+keyof

interface API {

  '/user': { name: **string** },

  '/menu': { foods: **Food**[] },}

const get = <URL extends keyof API>(url: URL): Promise<API[URL]>=> {

 return fetch(url).then(res => res.json())

}

图片2.png

6.巧用

DeepReadonly  type DeepReadonly<T> = {
  readonly [P in keyof T]: DeepReadonly<T[P]>;
}
const a = { foo: { bar: 22 } }

const b = a as DeepReadonly<typeof a>

A.foo.bar=33//ok

b.foo.bar=33//不ok

7.as的用法

8.interface Test{

}