Reading command line arguments

JavaScript:
Reading command line arguments

How to:

Here’s the straight-up way to do it in Node.js:

// process.argv contains command line arguments
const args = process.argv.slice(2);

console.log(args);

// Run this script with: node yourscript.js firstArg secondArg

Sample output if you run node yourscript.js pineapple 42:

['pineapple', '42']

Using a package like yargs makes life easier, letting you define and access arguments by name.

// Install with npm install yargs
const yargs = require('yargs/yargs');
const { hideBin } = require('yargs/helpers');
const argv = yargs(hideBin(process.argv)).argv;

console.log(argv);

// Run this with: node yourscript.js --fruit pineapple --number 42

And you’d get:

{ fruit: 'pineapple', number: '42' }

Clean and clear, with named parameters.

Deep Dive

Way back, arguments were read in C using argc and argv in the main function. In Node.js, process.argv is the go-to. It’s an array where the first element is the path to the node executable, the second is the script file name, and the rest are your actual arguments.

yargs is nifty for complex apps: it parses arguments into a handy object, manages defaults, and even auto-generates help messages.

There’s also the minimist package, a lighter alternative to yargs, if you’re into minimalism.

Deep down, Node.js uses V8’s process.binding('options') for parsing which isn’t exposed to the average user. This internal method packs tons of utility under the hood, managing the parsing and retrieval of command line options.

JavaScript:Reading command line arguments

How to:

Deep Dive

See Also

JavaScript:
Reading command line arguments