Using node-sass watch option with npm run-script

Question

So I'm running tasks in npm package scripts but I want to pass the watch option in npm start.

This works:

"scripts": {
  "scss": "node-sass src/style.scss dist/style.css -w"
}

This doesn't compile, watch, or throw any error:

"scripts": {
  "scss": "node-sass src/style.scss dist/style.css",
  "start": "parallelshell \"npm run scss -- -w\""
}

Doesn't work without parallelshell either or without shorthand.

I assume the problem is the run-script is passing the extra argument in quotes, so the command comes out like:

node-sass src/style.scss dist/style.css "-w"

I'd like this to work without adding any dependencies. What am I missing?

Btw, I'm in Windows 10 with command prompt/git bash.

Solution 1

This is my setup for css building

"scripts": {
  "css": "node-sass src/style.scss -o dist",
  "css:watch": "npm run css && node-sass src/style.scss -wo dist"
},
"devDependencies": {
  "node-sass": "^3.4.2"
}

The -o flag sets the directory to output the css. I have a non-watching version "css" because the watching version "css:watch" ~doesn't build as soon as it's run~, it only runs on change, so I call

npm run css 

before calling

node-sass src/style.scss -wo dist

If you only want it to run on change, and not when first run, just use

"css:watch": "node-sass src/style.scss -wo dist"

Solution 2

Building on the previous answers, another option is to leverage NPM's custom script arguments to remain DRY by not repeating the build script arguments in the watch script:

"scripts": {
  "build:sass": "node-sass -r --output-style compressed src/style.scss -o dist",
  "watch:sass": "npm run build:sass && npm run build:sass -- -w"
}

In the above example, the watch:sass script works as follows:

1. Run the build:sass script. This will compile your CSS.
2. Run the build:sass script again, but this time include the -w flag. This will compile your CSS when one of your SASS file changes.

Notice the -- option used at the end of the watch:sass script. This is used to pass custom arguments when executing a script. From the docs:

As of [email protected], you can use custom arguments when executing scripts. The special option -- is used by getopt to delimit the end of the options. npm will pass all the arguments after the -- directly to your script.

Solution 3

Btw, here's my change:

"scss": "node-sass src/style.scss dist/style.css",
"start": "parallelshell \"npm run scss && npm run scss -- -w\"

Edit: Change was asynchronous script runs, for the initial compile and then with the watch flag.

Comments

[Evgeny Bobkin]

Please consider my answer( how-can-i-get-node-sass-watch-and-live-reload-to-work-from-a‌​-single-npm-script) on this one!

[ALI ATTALAOUI]

if you use vcode , I prefer to use extention watching sass live-server it's very useful way

[Ryan Metin]

Is there not a way to escape the double quotes it passes though? Like I said, this works: node-sass src/style.scss dist/style.css -w This doesn't: node-sass src/style.scss dist/style.css "-w" Thanks for the tips though. I'll use them for now.

[Ryan White]

You can escape the double quote using backslash. Like: \"-w\", this way the double quotes don't make the JSON invalid, but they show up when you are running the command in the terminal

[Ryan Metin]

I got that. I meant so that npm run scss -- -w doesn't pass node-sass src/style.css dist/style.scss "-w".

[Ryan Metin]

Wait... nevermind. I'm an idiot. Don't know why I thought changes weren't doing anything before. Thanks for the help.

[Rocco]

I had to change the second line to this for the watcher to work (parallelshell 2.0): "start": "parallelshell \"npm run scss\" \"npm run scss -- -w\""

[Ryan Metin]

Huh, I've got 2.0 as well. What if you run the tasks in sync, like: npm run scss & npm run scss -- -w. Works either way on my end..

[Rocco]

not for me - watcher did not actually remain in "watch" mode, so I stuck to parallelshell docs. Also meanwhile I created a "prewatch" task: "prewatch": "npm run scss"

[mikemaccana]

Could you edit and explain the answer? 'Here's my change' is pretty vague. What's parallelshell?

[Nicholas Petersen]

Dude, that's golden, thank you. FYI, for other node-sass options: npmjs.com/package/node-sass#command-line-interface

[Chukwuemeka Ihedoro]

warning From Yarn 1.0 onwards, scripts don't require "--" for options to be forwarded. In a future version, any explicit "--" will be forwarded as-is to the scripts. the script should be updated as "watch:sass": "npm run build:sass && npm run build:sass -w"