ts-node-dev

What is ts-node-dev?

ts-node-dev is a development tool for TypeScript that allows you to run and restart your TypeScript application automatically when files are modified. It combines the functionality of ts-node and nodemon, providing a seamless development experience for TypeScript projects.

What are ts-node-dev's main functionalities?

Automatic Restart

Automatically restarts the TypeScript application when any file in the project is modified. This is useful for development as it eliminates the need to manually restart the server after making changes.

ts-node-dev --respawn src/index.ts

Fast Compilation

Uses TypeScript's transpile-only mode to speed up the compilation process. This is useful for development environments where type checking can be deferred to a later stage.

ts-node-dev --transpile-only src/index.ts

Ignore Files

Allows you to specify files or directories to ignore for changes. This is useful for excluding large directories like node_modules from being watched, which can improve performance.

ts-node-dev --ignore-watch node_modules src/index.ts

Custom Compiler

Allows you to specify a custom TypeScript compiler. This is useful if you are using a TypeScript compiler with additional features or plugins.

ts-node-dev --compiler ttypescript src/index.ts

Other packages similar to ts-node-dev

nodemon

Nodemon is a utility that monitors for any changes in your source and automatically restarts your server. It is language-agnostic and can be used with JavaScript, TypeScript, and other languages. Unlike ts-node-dev, nodemon does not provide TypeScript compilation out of the box and requires additional setup to work with TypeScript.

ts-node

ts-node is a TypeScript execution environment and REPL for Node.js. It allows you to run TypeScript code directly without precompiling. However, it does not provide automatic restarts on file changes, which is a feature provided by ts-node-dev.

webpack

Webpack is a module bundler that can be used to compile TypeScript code and watch for changes. It is highly configurable and can be used with various plugins and loaders to achieve similar functionality to ts-node-dev. However, it is more complex to set up and configure compared to ts-node-dev.

README

ts-node-dev

Tweaked version of node-dev that uses ts-node under the hood.

It restarts target node process when any of required files changes (as standard node-dev) but shares Typescript compilation process between restarts. This significantly increases speed of restarting comparing to node-dev -r ts-node/register ..., nodemon -x ts-node ... variations because there is no need to instantiate ts-node compilation each time.

Install

yarn add ts-node-dev --dev

npm i ts-node-dev --save-dev

Usage

ts-node-dev [node-dev|ts-node flags] [ts-node-dev flags] [node cli flags] [--] [script] [script arguments]

So you just combine node-dev and ts-node options (see docs of those packages):

ts-node-dev --respawn --transpile-only server.ts

There is also short alias tsnd for running ts-node-dev:

tsnd --respawn server.ts

Look up flags and options can be used in ts-node's docs.

Also there are additional options specific to ts-node-dev:

• --ignore-watch - (default: []) - files/folders to be ignored by node-dev. But this behaviour is enhanced: it also supports regular expression in the ignore strings and will check absolute paths of required files for match.

• --deps - Also watch node_modules; by default watching is turned off

• --debug - Some additional [DEBUG] output

• --quiet - Silent [INFO] messages

• --interval - Polling interval (ms) - DOESN'T WORK CURRENTLY

• --debounce - Debounce file change events (ms, non-polling mode)

• --clear (--cls) - Will clear screen on restart

• --watch - Explicitly add arbitrary files or folders to watch and restart on change (list separated by commas, chokidar patterns)

• --exit-child - Adds 'SIGTERM' exit handler in a child process.

• --rs - Allow to restart with "rs" line entered in stdio, disabled by default.

• --notify - to display desktop-notifications (Notifications are only displayed if node-notifier is installed).

• --cache-directory - tmp dir which is used to keep the compiled sources (by default os tmp directory is used)

If you need to detect that you are running with ts-node-dev, check if process.env.TS_NODE_DEV is set.

Points of notice:

• If you want desktop-notifications you should install node-notifier package and use --notify flag.

• Especially for large code bases always consider running with --transpile-only flag which is normal for dev workflow and will speed up things greatly. Note, that ts-node-dev will not put watch handlers on TS files that contain only types/interfaces (used only for type checking) - this is current limitation by design.

• --ignore-watch will NOT affect files ignored by TS compilation. Use --ignore option (or TS_NODE_IGNORE env variable) to pass RegExp strings for filtering files that should not be compiled, by default /node_modules/ are ignored.

• Unknown flags (node cli flags are considered to be so) are treated like string value flags by default. The right solution to avoid ambiguity is to separate script name from option flags with --, for example:

  ts-node-dev --inspect -- my-script.ts
  

• The good thing is that ts-node-dev watches used tsconfig.json file, and will reinitialize compilation on its change, but you have to restart the process manually when you update used version of typescript or make any other changes that may effect compilation results.

Issues

If you have an issue, please create one. But, before:

• try to check if there exits alike issues.
• try to run your code with just ts-node
• try to run your code with --files option enabled (see ts-node docs)
• try to run it with --debug flag and see the output
• try to make create repro example

Versioning

Currently versioning is not stable and it is still treated as pre-release. You might expect some options API changes. If you want to avoid unexpected problems it is recommended to fixate the installed version and update only in case of issues, you may consult CHANGELOG for updates.

License

MIT.