How to resolve Node.js ES6 (ESM) Modules with the TypeScript Compiler (TSC). TSC doesn’t emit the correct file-ext

This is a confusing design choice in TypeScript.

In the short term you can work around it by specifying the output file:

in main.ts specify the .js extension and path:

import { testText } from './module1.js';
alert(testText);

This will pick up module.ts correctly, but output with the .js extension included.

Note that you also need to prefix local files with ./ as ‘bare’ module names are reserved for future use.