Simple TypeScript playground via node --watch

Now that Node.js has built-in support for TypeScript, we can use it as the foundation of a simple playground that lets us interactively explore TypeScript code.

A simple playground  #

This is the basic approach:

• We create a file playground.mts
  • The filename extension is .mts so that we don’t need a package.json file to tell Node.js that .ts means ESM module.
• We run the following command in a terminal:

  node --disable-warning=ExperimentalWarning --watch ./playground.mts
  

• We edit playground.mts. Whenever we save it, Node.js re-runs it and shows its output.

More configuration  #

Alas, we often need two additional files:

• A tsconfig.json with our preferred settings
• A package.json with "type":"module" so that we can use the filename extension .ts.

I have created the GitHub repository nodejs-type-stripping where both are already set up correctly.

Further reading  #

• The relevant Node.js command line options are:
  • --watch Watches a file and its imports for changes and re-runs the file whenever that happens.
  • --watch-path Overrides the default of watching the imports and tells Node.js which files to watch instead.
  • --watch-preserve-output Disables the clearing of the console before the file is re-run.
• 2ality blog post “Node’s new built-in support for TypeScript”