How to run TypeScript files from command line?

Question

I\'m having a surprisingly hard time finding an answer to this. With plain Node.JS, you can run any js file with node path/to/file.js, with CoffeeScript it\'s <

Answer 1

None of the other answers discuss how to run a TypeScript script that uses modules, and especially modern ES Modules.

First off, ts-node doesn't work in that scenario, as of March 2020. So we'll settle for tsc followed by node.

Second, TypeScript still can't output .mjs files. So we'll settle for .js files and "type": "module" in package.json.

Third, you want clean import lines, without specifying the .js extension (which would be confusing in .ts files):

import { Lib } from './Lib';

Well, that's non-trivial. Node requires specifying extensions on imports, unless you use the experimental-specifier-resolution=node flag. In this case, it would enable Node to look for Lib.js or Lib/index.js when you only specify ./Lib on the import line.

Fourth, there's still a snag: if you have a different main filename than index.js in your package, Node won't find it.

Transpiling makes things a lot messier than running vanilla Node.

Here's a sample repo with a modern TypeScript project structure, generating ES Module code.