typescript checkJs + node

anotherfile.d.ts

export interface AnotherfileStatic {
  validfunction(greeting: string);
}

declare const Anotherfile: AnotherfileStatic;

export default Anotherfile;

anotherfile.js

module.exports = {
  validfunction(greeting) {
    console.log(greeting);
  }
};

index.js

const anotherfile = require('./anotherfile');

anotherfile.validfunction('hello');

package.json

{
  "name": "tstest",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@types/node": "7.0.18",
    "typescript": "2.3.2"
  }
}

tsconfig.json

{
  "compilerOptions": {
    "noEmit": true,
    "module": "commonjs",
    "allowJs": true,
    "checkJs": true,
    "target": "es6",
    "types": [
      "node"
    ]
  }
}