javascript - 令人困惑的编译器错误 : Argument of type 'string' is not assignable to parameter of type

Question

我有一个包含可接受的 mime 类型的数组:

export const frontend = { 
  ...
  zipMimeTypes: [
    "application/zip",
    "application/x-zip-compressed",
    "multipart/x-zip",
  ],
} as const;

我想将它包含在另一个文件中并像这样使用它:

frontend.zipMimeTypes.includes(file.type)

但是，我的 TS 编译器提示 file.type

Argument of type 'string' is not assignable to parameter of type '"application/zip" | "application/x-zip-compressed" | "multipart/x-zip"'.

我只是这样做:

  [
    "application/zip",
    "application/x-zip-compressed",
    "multipart/x-zip",
  ].includes(file.type)

有效

Answer 1

问题出在 as const 中。相反，您可以定义一个接口(interface)来与前端一起使用:

interface Frontend {
  zipMimeTypes: string[];
}
const frontend: Frontend = {
  zipMimeTypes: [
    "application/zip",
    "application/x-zip-compressed",
    "multipart/x-zip"
  ]
};