What is the 'default' part for an imported Node.js module, generated from Typescript?

Question

In a typescript file I have a import of the filesystem and path Node modules. I use them in a pretty standard way, like:

const workDir = path.join(outputDir, "process-specs");.

When I transpile that using tsc it generates this line instead:

var workDir = path_1.default.join(outputDir, "process-specs");

The problem with that is the additional default member of the path module variable. I don't see it in the Node.js path documentation and wonder why tsc adds that and what this is about.

Answer 1

It's aping the default export of es2015 modules: when you do import foo from 'foo'; you are importing the default export of the foo module.

// foo.ts
export default foo;

// otherfile.ts
import foo from 'foo';

vs a named export

// foo.ts
export foo;

// otherfile.ts
import { foo } from 'foo';

If this is only running in node.js and not the browser you can just use require like normal, e.g. const fs = require('fs');. You'll need to install node typings so the compiler understands it:

npm install --save-dev @types/node

Answer 2

allowSyntheticDefaultImports in tsconfig.json is why default was generated for tsc. and importHelpers, esModuleInterop assume more advanced way to use.