🧩 Node Arg Parser

A simple, chainable command-line argument parser for Node.js CLI tools. Supports type validation, short & long args, and automatic help display.

📦 Installation

Install via npm:

npm install node-arg-parser

🧠 Features

✅ Short and long flags (e.g., -f and --file)
✅ Type validation (String, Number, Boolean)
✅ Required or optional arguments
✅ Built-in --help flag support
✅ Automatically aligned usage help

🚀 Getting Started

Step 1: Import the Parser

import ArgParser from 'node-arg-parser';
// or for CommonJS:
// const ArgParser = require('node-arg-parser');

Step 2: Define Your Arguments

const parser = new ArgParser();

parser
  .add('-f', '--file')
  .acceptType(String)
  .setDescription('The path to the input file')
  .required();

parser
  .add('-v', '--verbose')
  .acceptType(Boolean)
  .setDescription('Enable verbose mode');

parser
  .add('-n', '--number')
  .acceptType(Number)
  .setDescription('A numeric input');

Step 3: Parse Arguments

const args = parser.parse();
console.log(args);

Step 4: Run via CLI

node app.js --file input.txt --verbose true --number 123

✅ Output:

{
  "file": "input.txt",
  "verbose": true,
  "number": 123
}

🔍 Using --help

You don’t need to configure this manually. Just run:

node app.js --help

🧾 Output:

Usage:

  -f  --file       The path to the input file
  -v  --verbose    Enable verbose mode
  -n  --number     A numeric input

📘 Full API Reference

add(short, long)

Defines a new argument.

• short: e.g. -f
• long: e.g. --file

Returns a chainable object.

.acceptType(type)

Defines expected type: String, Number, or Boolean

.setDescription(text)

Sets a human-readable description (used in help output)

.required([true|false])

Marks argument as required (default is false)

🧪 Example with Validation

parser
  .add('-p', '--port')
  .acceptType(Number)
  .setDescription('Port to run the server on')
  .required();

# Valid
node app.js --port 3000

# Invalid
node app.js --port abc
# Error: Argument --port must be a number

🧑‍💻 Author

Jatin Gohil
GitHub: @lkjatinc669

🐞 Issues & Contributions

Found a bug or want to contribute? Open an issue or PR at:

👉 https://github.com/lkjatinc669/node-arg-parser/issues

📄 License

Licensed under the ISC License