Node watch mode and TypeScript

You might have heard that Node now has watch mode. It watches the files you're saving and re-runs the node command automatically. Example:

// example.js

function c2f(c) {
  return (c * 9) / 5 + 32;
}
console.log(c2f(0));

Now, run it like this:

❯ node --watch example.js
32
Completed running 'example.js'

Edit that example.js and the terminal will look like this:

Restarting 'example.js'
32
Completed running 'example.js'

(even if the file didn't change. I.e. you just hit Cmd-S to save)

Now, node doesn't understand TypeScript natively, yet. So what are you to do: Use @swc-node/register! (see npmjs here)
You'll need to have a package.json already or else use globally installed versions.

Example, using npm:

npm init -y 
npm install -D typescript @swc-node/register
npx tsc --init

Now, using:

// example.ts

function c2f(c: number) {
  return (c * 9) / 5 + 32;
}
console.log(c2f(123));

You can run it like this:

❯ node --watch --require @swc-node/register example.ts
253.4
Completed running 'example.ts'