如何为module.exports导出的函数及相关接口编写对应的.d.ts类型定义文件

Let's fix your .d.ts file so it properly matches your CommonJS export pattern (module.exports = function foo()) while supporting both clean ES module imports and exporting your required types. Here's the right approach:

Working Type Definition #

declare module 'mymodule' {
  // Export your custom types first
  export type Language = 'it' | 'es' | 'de';
  export type Platform = 'linux' | 'winzoz';

  // Declare the function signature
  function foo(language: Language, platform: Platform, milliseconds?: number): void;

  // Support both CommonJS require() and ES module import (with esModuleInterop)
  export default foo;
  export = foo;
}

Why This Works #

Let's break down why this solves your issues:

• export = foo directly maps to your CommonJS module.exports = foo pattern, so const foo = require('mymodule') works without any extra config.
• export default foo adds support for ES module-style import foo from 'mymodule' when you enable esModuleInterop in your tsconfig.json (more on that below).
• Your Language and Platform types are exported at the module level, so you can import them separately just like any other TypeScript type.

Import Examples #

CommonJS (no config needed) #

const foo = require('mymodule');
foo('it', 'linux', 1000);

// Importing types (TypeScript only)
const foo = require('mymodule');
import type { Language, Platform } from 'mymodule';
const lang: Language = 'es';

ES Module (with esModuleInterop enabled) #

import foo from 'mymodule';
import type { Language, Platform } from 'mymodule';

const lang: Language = 'de';
foo(lang, 'winzoz');

Fixing Your Previous Attempts #

Let's go over why your earlier tries didn't work:

1. First attempt (export function foo):
   This declares a module that exports a named foo function, but your actual JS module exports the function as the entire module itself. So you'd have to import it as import { foo } from 'mymodule', which doesn't match your CommonJS export.

2. Second attempt (export default foo):
   Without esModuleInterop, TypeScript treats ES module import statements strictly and expects your CommonJS module to have a default property (which it doesn't—your module is the function itself).

3. Third attempt (export = foo):
   This works for CommonJS, but requires the clunky import foo = require('mymodule') syntax for ES modules. Adding export default foo alongside it fixes this, and your types still remain exportable.

Recommended TSConfig Settings #

To make ES module imports work smoothly with CommonJS modules, add these to your tsconfig.json:

{
  "compilerOptions": {
    "esModuleInterop": true,
    "allowSyntheticDefaultImports": true
  }
}

• esModuleInterop tells TypeScript to handle CommonJS modules as if they have a default export when using ES import.
• allowSyntheticDefaultImports lets you write import foo from 'mymodule' without TypeScript throwing an error about missing a default export.

内容的提问来源于stack exchange，提问作者EuberDeveloper