javascript - 输入 { [键 : string]: string } is not assignable to type { [key: string]: string } | 'undefined'

Question

我正在尝试创建一个函数，通过添加一个 cookie 从 node-fetch 包装 fetch:

import fetch from 'node-fetch';

const api = (path: string, params: RequestInit) => fetch(
  path, {
    ...(params || {}),
    headers: {
      ...(params?.headers || {}),
      cookie: 'mycookie'
    },
  }
)

我在 headers 上收到此错误:

(property) RequestInit.headers?: string[][] | Headers | {
    [key: string]: string;
} | undefined
Type '{ cookie: string; append(name: string, value: string): void; delete(name: string): void; get(name: string): string | null; has(name: string): boolean; set(name: string, value: string): void; forEach(callbackfn: (value: string, key: string, parent: Headers) => void, thisArg?: any): void; } | { ...; } | { ...; }' is not assignable to type 'string[][] | Headers | { [key: string]: string; } | undefined'.
  Type '{ cookie: string; append(name: string, value: string): void; delete(name: string): void; get(name: string): string | null; has(name: string): boolean; set(name: string, value: string): void; forEach(callbackfn: (value: string, key: string, parent: Headers) => void, thisArg?: any): void; }' is not assignable to type 'string[][] | Headers | { [key: string]: string; } | undefined'.
    Type '{ cookie: string; append(name: string, value: string): void; delete(name: string): void; get(name: string): string | null; has(name: string): boolean; set(name: string, value: string): void; forEach(callbackfn: (value: string, key: string, parent: Headers) => void, thisArg?: any): void; }' is not assignable to type 'undefined'.ts(2322)

最后它说它不能分配给类型“undefined”。我想如果一个类型的值保证是它的联合类型之一，它不应该提示。

Answer 1

node-fetch 定义了自己的类型，这些类型与 DefinitelyTyped 类型定义不兼容(node-fetch 可能是最新的)。如果两者都可用，您通常应该使用库自己的类型而不是 DefinitelyTyped。

https://github.com/node-fetch/node-fetch/blob/master/@types/index.d.ts#L60 https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/node-fetch/index.d.ts#L48

库的类型有 RequestInit 的 body 属性为 BodyInit | null，因此将其标记为 null 的能力使其与其他类型不兼容。只需导入即可使用库的类型:

import fetch, { RequestInit } from 'node-fetch';