Sending command line arguments to npm script

The scripts portion of my package.json currently looks like this:
"scripts": {
"start": "node ./script.js server"
}


...which means I can run npm start to start the server. So far so good.

However, I would like to be able to run something like npm start 8080 and have the argument(s) passed to script.js (e.g. npm start 8080 => node ./script.js server 8080). Is this possible?

npm 2 and newer

It's possible to pass args to npm run since npm 2 (2014). The syntax is as follows:

npm run [-- ]

Note the -- separator, used to separate the params passed to npm command itself, and the params passed to your script. (This is a common convention used by various command line tools).

With the example package.json:
"scripts": {
"grunt": "grunt",
"server": "node server.js"
}


here's how to pass the params to those scripts:
npm run grunt -- task:target // invokes grunt task:target
npm run server -- --port=1337 // invokes node server.js --port=1337


Note: If your param does not start with - or --, then having an explicit -- separator is not needed; but it's better to do it anyway for clarity.
npm run grunt task:target // invokes grunt task:target


Note below the difference in behavior (test.js has console.log(process.argv)): the params which start with - or -- are passed to npm and not to the script, and are silently swallowed there.
$ npm run test foobar
['C:\\Program Files\\nodejs\\node.exe', 'C:\\git\\myrepo\\test.js', 'foobar']

$ npm run test -foobar
['C:\\Program Files\\nodejs\\node.exe', 'C:\\git\\myrepo\\test.js']

$ npm run test --foobar
['C:\\Program Files\\nodejs\\node.exe', 'C:\\git\\myrepo\\test.js']

$ npm run test -- foobar
['C:\\Program Files\\nodejs\\node.exe', 'C:\\git\\myrepo\\test.js', 'foobar']

$ npm run test -- -foobar
['C:\\Program Files\\nodejs\\node.exe', 'C:\\git\\myrepo\\test.js', '-foobar']

$ npm run test -- --foobar
['C:\\Program Files\\nodejs\\node.exe', 'C:\\git\\myrepo\\test.js', '--foobar']


The difference is clearer when you use a param actually used by npm:
$ npm test --help // this is disguised npm --help test
npm test [-- ]

aliases: tst, t


To get the parameter value, see this question. For reading named parameters, it's probably best to use a parsing library like yargs or minimist; nodejs exposes process.argv globally, containing command line parameter values, but this is a low-level API (whitespace-separated array of strings, as provided by the operating system to the node executable).

Stack Overflow Q#11580961, score: 2052