How Can I Pass Command Line Arguments to My npm Scripts?

Sending Command Line Arguments to npm Script

When it comes to npm scripts, there's often a desire to pass arguments from the command line to the script being executed. Let's delve into how to accomplish this.

npm 2 and Newer

Starting with npm 2, passing arguments is straightforward:

npm run <command> [-- <args>]

The crucial element here is the -- separator. It distinguishes between arguments intended for npm and those meant for your script.

For example, with the package.json snippet below:

{
  "scripts": {
    "grunt": "grunt",
    "server": "node server.js"
  }
}

You can pass arguments as follows:

npm run grunt -- task:target  // invokes `grunt task:target`
npm run server -- --port=1337 // invokes `node server.js --port=1337`

Note: Explicit -- separation is recommended even when arguments don't start with - or --. Consider:

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

In contrast, using explicit -- removes ambiguity:

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

To access parameter values within your script, refer to process.argv. Alternatively, consider using parsing libraries such as yargs or minimist for greater flexibility in handling arguments, including named parameters.

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