用于打字的TypeScript外部节点模块声明文件

Question

I have a Node.js module ( index.js ) that has been transpiled with Babel to the code as follows:

// My stuff ...
var fs = require("fs");
var path = require("path");

exports.fileContent = fs.readFileSync(
  path.join(__dirname, "file.txt"),
  'utf8'
);

// Babel compiler stuff ...
Object.defineProperty(
  exports,
  "__esModule",
  { value: true }
);

// My stuff again ...
exports.default = exports.fileContent;

Usage in Node.js would be:

var myModule = require("my-module");

doSomethingWithIt( myModule.fileContent );

As far as I understand, I need to create a .d.ts declaration file and reference it in the typings field in my package.json . And also, this declaration file has to be a module. So my first approach after reading several tutorials about this topic was:

// index.d.ts

declare module "my-module" {
  export const fileContent: string;
  export default fileContent;
}

But sadly, this was a fail:

[...] error TS2656: Exported external package typings file 'index.d.ts' is not a module. [...]

My next approach was to get rid of the declare module thing:

export const fileContent: string;
export default fileContent;

This works for me, but however feels wrong as I did not find any .d.ts example file that is not using the declare stuff. I also noticed that I should not use export default in a namespace/module, which leads me to the point where I don't understand how to declare the default export of my module at all.

Here are my questions:

• How do I do this the right way?
• How can I make sure that TypeScript recognizes the default property?
• Do I need to use the declare module stuff?
• Do I need to declare the imports ( fs and path )?

---

Edit:

After a bit more researching and fiddling, I think I have found the solution by myself. As far as I understand, the external module description/declaration has to be a module—which means that it has to import or export something: In this case, it has to export the declaration and the declared constant as the default export as well:

export declare const fileContent: string;
export default fileContent;

Answer 1

error TS2656: ... is not a module happens when trying to use ES6 style imports and the definition does not export a module.

I suggest changing your definition to

declare module MyModule {
    export const fileContent: string;
}

declare module "my-module" {
    export default MyModule
}

Since this definition is now "default exporting" a module, it can be imported using the default ES6 import syntax

import MyModule from "my-module"

Then use it

MyModule.fileContent...