Using npm to build my typescript/node project

Question

I have a project written in TypeScript and running on Node. I'm really struggling to write the script with npm to get it running for development. What I trying to do is:

clean the /dist folder
if a .ts change, compile it into /dist and restart node

Here is my 1st attempt, from the scripts section of my package.json:

"clean": "rimraf dist/**/*",
"build": "tsc",
"watch:start": "npm run clean && nodemon -e ts --exec \"npm run start\"",
"start": "npm run build && node dist/index.js"

If I start my project with npm run watch:start, it got stuck in a loop:

npm run watch:start
> nodemon -e ts --exec "npm run start"

[nodemon] 1.11.0
[nodemon] to restart at any time, enter `rs`
[nodemon] watching: *.*
[nodemon] starting `npm run start`
[nodemon] restarting due to changes...
[nodemon] restarting due to changes...
[nodemon] starting `npm run start`
[nodemon] restarting due to changes...
[nodemon] restarting due to changes...

Here is my 2nd attempt, using npm-run-all to run several task in parallel:

"clean": "rimraf dist/**/*",
"build": "tsc",
"watch:start": "npm-run-all clean build --parallel --race watch:build watch:serve --print-label",
"watch:build": "tsc -w",
"watch:serve": "nodemon dist/index.js"

This one works better but it still restart node several time at startup.

Suggestions and improvements welcome !

You should first run tsc to compile your typescript app and run tsc -w and your server concurrently. — Shane
– Shane, Commented Jul 31, 2017 at 13:18
That what I do in my 2nd attempt. I added the "build" part after the "clean" in my 1st attempt and got the same result. "tsc -w" build all the .ts files when started anyway. — Christophe Le Besnerais
– Christophe Le Besnerais, Commented Jul 31, 2017 at 13:34

Shane · Accepted Answer · 2017-07-31 15:02:48Z

You can use tsc-watch, which omits the use of nodemon and runs when any changes affect the typescript source of your app.

"scripts": {
  "dev": "tsc-watch --onSuccess \"npm start\" ",
  "start": "node index.js"
}

It has a success handler --onSuccess which restarts the server everytime a change is made to the typescript source.

npm run dev

index.js

console.log('node run')

setTimeout(() => console.log(Math.random() * 1000.0), 1000);

console

npm run dev    
> tsc && concurrently "npm run node-tsc:w"

npm WARN invalid config loglevel="notice"

> [email protected] node-tsc:w C:\Users\Shane\Desktop\so
> tsc-watch --onSuccess "node index.js"

16:49:31 - Compilation complete. Watching for file changes.


node run
709.2226373633507
16:49:36 - File change detected. Starting incremental compilation...


16:49:37 - Compilation complete. Watching for file changes.


node run
974.6349162351444
16:49:41 - File change detected. Starting incremental compilation...


16:49:41 - Compilation complete. Watching for file changes.


node run
935.9043001938232

Node is restarted after changing the typecript source.

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