Dynamically pass a file name to my NPM script as a command line arg

Question

Here is some code.

I have tried using -- and passing as an env variable i.e. --script=myscript.js. The code I have linked is getting me very close but I need to remove the space between the script name.

"scripts": {
    "script": "nodemon --exec babel-node ./scripts/${*}",
  }

then I run in console:

npm run script populateVehicleData.js.

That results in this

[nodemon] 1.18.7
[nodemon] to restart at any time, enter `rs`
[nodemon] watching: *.*
[nodemon] starting `babel-node ./scripts/ populateVehicleData.js`
internal/modules/cjs/loader.js:657
    throw err;
    ^

Error: Cannot find module '/Users/jakeneels/work/api/scripts/'

Notice that the script is executing 'babel-node ./scripts/ populateVehicleData.js'. Why is the space there? how do I get rid of it?

I expect to execute babel-node ./scripts/populateVehicleData.js and run my script whatever its name might be. instead i get babel-node ./scripts/ populateVehicleData.js causing npm to not find the file due to the space between scripts/ and populateVehicleData.js.

Wrap your npm script in a shell function and utilize ${1} to reference the filename (i.e. the first positional parameter/arg) passed. For instance change your npm script to: "script": "func() { nodemon --exec babel-node ./scripts/${1}; }; func", - then run following command: npm run script populateVehicleData.js. Or run npm run script -- populateVehicleData.js. (Note the double hyphens -- used in 2nd invocation, i.e. getopt to delimit end of options). — RobC
– RobC, Commented May 8, 2019 at 8:58
You could also consider changing your script to utilize a default filename. For instance: "script": "func() { nodemon --exec babel-node ./scripts/${1:-somefile.js}; }; func", - Now if you run npm run script (i.e. without a filename argument) it will default to ./scripts/somefile.js . However, if you run npm run script populateVehicleData.js it will use the file at ./scripts/populateVehicleData.js instead. — RobC
– RobC, Commented May 8, 2019 at 9:05

William Neely · Accepted Answer · 2022-07-22 19:33:45Z

1

You can also set the file name as an env variable and read it from there.

"scripts": {
"script": "nodemon --exec babel-node ./scripts/${fileName}",
}

and then

fileName=populateVehicleData npm run script

answered Jul 22, 2022 at 19:33

William Neely

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