npm sub script with command line parameters

Question

I have some npm scripts that look like this:

"scripts": {
 "exec:dev": "export NODE_ENV=development && npm run exec",
 "exec:stage": "export NODE_ENV=stage && npm run exec",
 "exec:prod": "export NODE_ENV=production && npm run exec",
 "exec": "node myapp.js"
}

I'd like to pass some command line arguments to myapp.js but this does not work:

npm run exec:prod -- -a 123 -b 456

This is apparently due to the fact that the exec:prod script is calling the exec script and apparently not passing along the command line parameters. Is there any way to achieve this while keeping the nested script calls?

Answer 1

To explicitly tell the exec script to pass along the arguments it gets, include another --.

Instead of:

npm run exec:prod -- -a 123 -b 456

try:

npm run exec:prod -- -- -a 123 -b 456

---

• The first double dash tells the exec:dev script, "these args aren't for you, pass them along to the exec script".

• The second double dash tells the exec script, "these args aren't for you, pass them along to node myapp.js".

Answer 2

If you want to keep the npm run command that you enter via the CLI the same as per your question. (i.e. avoid adding yet another npm special option (--) to it, as per @MikePatrick 's answer).

Change your npm-scripts to the following instead:

"scripts": {
 "exec:dev": "export NODE_ENV=development && npm run exec --",
 "exec:stage": "export NODE_ENV=stage && npm run exec --",
 "exec:prod": "export NODE_ENV=production && npm run exec --",
 "exec": "node myapp.js"
}

Note: the npm special option (--) added to the end of the first three scripts.

---

Demo

For demonstration purposes, lets say myapp.js is as follows:

myapp.js

const args = (process.argv.slice(2));
const nodeEnv = process.env.NODE_ENV;
console.log(nodeEnv);
console.log(args);

Testing:

• Running npm run exec:dev -- -a 123 -b 456 prints:

  development

  [ '-a', '123', '-b', '456' ]

• Running npm run exec:stage -- -a 123 -b 456 prints:

  stage

  [ '-a', '123', '-b', '456' ]

• Running npm run exec:prod -- -a 123 -b 456 prints:

  production

  [ '-a', '123', '-b', '456' ]

---

Further info

The docs for npm-run-script describe the npm special option (--) as follows:

... 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 ... The arguments will only be passed to the script specified after npm run and not to any pre or post script.