Passing key value arguments from npm

Question

So I'm struggling with passing command line option arguments from npm to a node script. I can pass options themselves, but not as key value pairs.

For my package.json I have:

"scripts": {
   "test": ". ./.env; node app.js --"
 },

(my understanding is that for npm you need to include and extra "--" to pass arguments) and in my app.js I have:

const { argv, options } = require('yargs');
console.log(argv._);

When I run

$ npm run test FOO BAR

I get:

[ 'FOO', 'BAR' ]

great, that worked, but if I try

$ npm run test FOO --BAR 99RedBalloons

I get:

[ 'FOO', '99RedBallons' ]

and

$ npm run test FOO --BAR=99RedBallons gives me:

[ 'FOO' ]

Wha? So, my question really is, using "run npm <>" and I assume yargs (since I believe that is the most popular package), how can I arrive with a arg._ of ["FOO", "Bar" : "99RedBalloons"].

Thanks!

There something weird to me how npm is passing command line arguments to the node script — Huckleberry Carignan
– Huckleberry Carignan, Commented Nov 6, 2018 at 16:17
I thought you wanted the exact result you say in your comment and the end of your question. — Mark
– Mark, Commented Nov 7, 2018 at 0:13

TGrif · Accepted Answer · 2018-11-06 19:44:33Z

Yes, you are right, according to the npm documentation, you must pass extra " -- " to specify arguments to an npm script, but you do not pass it at the right place.

You do not need to pass it at the end of your package.json "test" script, but directly in the command line which call your script.

This way, npm understand it is arguments for your script and not for the npm command itself:

// cli
$ npm run test -- FOO --BAR 99RedBalloons    // "--" before arguments
  /* or */
$ npm run test -- FOO --BAR=99RedBalloons

// package.json
"scripts": {
   "test": ". ./.env; node app.js"
 }

// app.js
const { argv } = require('yargs');
console.log(argv);

// -> { _: [ 'FOO' ], BAR: '99RedBalloons', '$0': 'app.js' }

I did not find a yargs built-in option to do it, but alternatively, if you want all your arguments in the _ array variable, you can do something like this:

for (let cmd in argv)
  if (cmd !== '$0' && cmd !== '_')
    argv._[cmd] = argv[cmd]

console.log(argv._)

// -> [ 'FOO', BAR: '99RedBalloons' ]

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