CLI Flag Parser

This is a simple and lightweight CLI flag parser for Node.js that allows you to easily define and parse command-line flags.

Features

• Register Flags: Define flags with or without default values.
• Parse Arguments: Automatically parse and retrieve the values of the flags passed via the command line.
• Boolean Flags: Supports flags that can be toggled with a --flag syntax.

Installation

npm install cli-flag-parser

Usage

Registering Flags

Before parsing the arguments, you must register the flags that your application will accept. You can register a flag with or without a default value.

const flags = require("cli-flag-parser");

// Registering flags
flags.registerFlag("name", "Name of the person")
     .registerFlag("age", "Age of the person", "21");

Parsing Arguments

Once the flags are registered, you can parse the command-line arguments using the parse() function.

const parsedFlags = flags.parse();
console.log(parsedFlags);

Example

Suppose you run your script with the following command:

node yourScript.js --name=John --age 30 --verbose -d --xyz=no

Here’s how you can use the parser to interpret the arguments:

const flags = require("cli-flag-parser");

// Registering flags
flags.registerFlag("name", "name of person")
    .registerFlag("age", "age of person")
    .registerFlag("run", "run", true)
    .registerFlag("verbose", "verbose boolean flag")
    .registerFlag("d", "d boolean flag");

// Parsing the command-line arguments
const parsedFlags = flags.parse();
console.log(parsedFlags);

Output:
{
    "name": "John",
    "age": "30",
    "run": true,  // defaultValue
    "verbose": true,
    "d": true
}

Note: 'xyz' is not present in the output because it was not registered.

API Reference

registerFlag(flag, description, defaultValue)

• flag (string, required) - The name of the flag.
• description (string, required)- A description of what the flag does
• defaultValue (any, optional) - Default value of flag.

parse()

• Parses the command-line arguments and returns an object with the flag names as keys and their corresponding values.

help()

• Print the help text to the console.

showHelp()

• Print help text to the console and exit with error.

unregisterFlags()

• Unregister all the flags.