[typescript] How to watch and reload ts-node when TypeScript files change

I'm trying to run a dev server with TypeScript and an Angular application without transpiling ts files every time. I found that I can do the running with ts-node but I want also to watch .ts files and reload the app/server as I would do with something like gulp watch.

If you are having issues when using "type": "module" in package.json (described in https://github.com/TypeStrong/ts-node/issues/1007) use the following config:

{
  "watch": ["src"],
  "ext": "ts,json",
  "ignore": ["src/**/*.spec.ts"],
  "exec": "node --loader ts-node/esm --experimental-specifier-resolution ./src/index.ts"
}

or in the command line

nodemon --watch "src/**" --ext "ts,json" --ignore "src/**/*.spec.ts" --exec "node --loader ts-node/esm --experimental-specifier-resolution src/index.ts"

I would prefer to not use ts-node and always run from dist folder.

To do that, just setup your package.json with default config:

....
"main": "dist/server.js",
  "scripts": {
    "build": "tsc",
    "prestart": "npm run build",
    "start": "node .",
    "dev": "nodemon"
  },
....

and then add nodemon.json config file:

{
  "watch": ["src"],
  "ext": "ts",
  "ignore": ["src/**/*.spec.ts"],
  "exec": "npm restart"
}

Here, i use "exec": "npm restart"
so all ts file will re-compile to js file and then restart the server.

To run while in dev environment,

npm run dev

Using this setup I will always run from the distributed files and no need for ts-node.

add this to your package.json file

scripts {
"dev": "nodemon --watch '**/*.ts' --exec 'ts-node' index.ts"
}

and to make this work you also need to install ts-node as dev-dependency

yarn add ts-node -D

run yarn dev to start the dev server

This works for me:

nodemon src/index.ts

Apparently thanks to since this pull request: https://github.com/remy/nodemon/pull/1552

Here's an alternative to the HeberLZ's answer, using npm scripts.

My package.json:

  "scripts": {
    "watch": "nodemon -e ts -w ./src -x npm run watch:serve",
    "watch:serve": "ts-node --inspect src/index.ts"
  },

• -e flag sets the extenstions to look for,
• -w sets the watched directory,
• -x executes the script.

--inspect in the watch:serve script is actually a node.js flag, it just enables debugging protocol.

you could use ts-node-dev

It restarts target node process when any of required files changes (as standard node-dev) but shares Typescript compilation process between restarts.

Install

yarn add ts-node-dev --dev

and your package.json could be like this

"scripts": {
  "test": "echo \"Error: no test specified\" && exit 1",
  "tsc": "tsc",
  "dev": "ts-node-dev --respawn --transpileOnly ./src/index.ts",
  "prod": "tsc && node ./build/index.js"
}

Specifically for this issue I've created the tsc-watch library. you can find it on npm.

Obvious use case would be:

tsc-watch server.ts --outDir ./dist --onSuccess "node ./dist/server.js"

Add "watch": "nodemon --exec ts-node -- ./src/index.ts" to scripts section of your package.json.

Another way could be to compile the code first in watch mode with tsc -w and then use nodemon over javascript. This method is similar in speed to ts-node-dev and has the advantage of being more production-like.

 "scripts": {
    "watch": "tsc -w",
    "dev": "nodemon dist/index.js"
  },

i did with

"start": "nodemon --watch 'src/**/*.ts' --ignore 'src/**/*.spec.ts' --exec ts-node src/index.ts"

and yarn start.. ts-node not like 'ts-node'

I've dumped nodemon and ts-node in favor of a much better alternative, ts-node-dev https://github.com/whitecolor/ts-node-dev

Just run ts-node-dev src/index.ts