Table of Contents

• Overview
  • Why argvex?
  • Key Features
• Getting started
  • How to install
  • How to use
  • Aliases
  • POSIX-flavoured
  • Repeating flags
  • Strict Mode
• Examples of common patters
  • Case with required flags
  • Case with default values
  • Case with value coercion
  • Case with error handling

Overview

Why argvex?

You want to roll-your-own CLI, but argument parsing is such a headache?
Let argvex handle the annoying part, and nothing else.

argvex is a minimalist argument parser that stays out of your way with little to no API, so you can keep full control, define your own rules, and avoid framework baggage.

Key Features

Getting started

argvex gives you a structured view of your command-line input — flags, values, and operands — without forcing schemas, coercion, or assumptions.

How to install

npm install argvex

How to use

You can just call argvex() to get structured process.argv output.

brewer brew espresso --size medium --shots 3 --milk none --temperature 92 --crema thick

import argvex from 'argvex'

const args = argvex()
// args -> { _: [ "brewer", "brew", "espresso" ], "size": [ "medium" ], shots: [ "3" ], milk: [ "none" ], temperature: [ "92" ], crema: [ "thick" ] }

A GNU-flavoured value assign using "=" works too!

brewer brew cappuccino --size=large --shots=2 --milk=steamed --foam=thick

import argvex from 'argvex'

const args = argvex()
// args -> { _: [ "brewer", "brew", "cappuccino" ], "size": [ "large" ], shots: [ "2" ], milk: [ "steamed" ], foam: [ "thick" ] }

When it comes to boolean flags, just check for their presence.

import argvex from 'argvex'

const args = argvex()
if (!!args.decaf) {
    console.log("Making a decaf coffee!")
}

You can use standalone short flags or use them in groups.

brewer brew americano -qs -m water -t 85

import argvex from 'argvex'

const args = argvex()
// args -> { _: [ "brewer", "brew", "americano" ], "q": [], "s": [], m: [ "water" ], t: [ "85" ] }

Use -- (end-of-options delimiter) to separate flags from operands that might look like flags.

brewer brew --milk oat -- --not-a-flag latte

import argvex from 'argvex'

const args = argvex()
// args -> { _: [ "brewer", "brew", "--not-a-flag", "latte" ], milk: [ "oat" ] }

Aliases

While you can code your own support for aliases easily, argvex can handle those out-of-the-box if you pass a minimal schema to it.

brewer brew mocha -d -m oat -c dark

import argvex from 'argvex'

const schema = [
  { name: "decaf", alias: "d" },
  { name: "milk", alias: "m" },
  { name: "chocolate", alias: "c" }
]
const args = argvex({ schema })
// args -> { _: [ "brewer", "brew", "mocha" ], "decaf": [], milk: [ "oat" ], chocolate: [ "dark" ] }

POSIX-flavoured

While argvex aims at being a minimalist tool, it can support most of the POSIX-flavoured syntax if you pass a schema to it.

brewer brew -dsmedium -h2 macchiato

import argvex from 'argvex'

const schema = [
  { name: "decaf", alias: "d", arity: 0 },
  { name: "size", alias: "s", arity: 1 },
  { name: "shots", alias: "h", arity: 1 },
]
const args = argvex({ schema })
// args -> { _: [ "brewer", "brew", "macchiato" ], "decaf": [], size: [ "medium" ], shots: [ "2" ] }

Repeating flags

By default, repeating a flag will override its previous value. If you want values to accumulate instead, enable additive mode.

brewer brew flat-white --milk steamed --milk foamed --milk microfoam

import argvex from 'argvex'

const schema = [
  { name: "milk", arity: 3 },
]
const args = argvex({ schema, additive: true })
// args -> { _: [ "brewer", "brew", "flat-white" ], milk: [ "steamed", "foamed", "microfoam" ] }

Strict Mode

You may force argvex to throw an error whenever unexpected flag or value gets passed.

brewer brew cortado --size small --shots 1 --no-pay

import argvex from 'argvex'

const schema = [
  { name: "size", arity: 1 },
  { name: "shots", arity: 1 },
]
const args = argvex({ schema, strict: true })
// args -> ArgvexError

Examples of common patters

argvex doesn't try to do anything more than parsing itself, so it's up to you how you want to handle the rest.
Here are some common patterns you might find useful.

Case with required flags

Sometimes you need to ensure certain flags are provided. You can check for their presence and throw an error if they're missing.

import argvex from 'argvex'

const args = argvex()

if (!args.temperature) {
    throw new Error('You must provide "--temperature" flag first.')
}

Case with default values

When optional flags aren't provided, you can set sensible defaults.

import argvex from 'argvex'

const args = argvex()

if (!args.milk) {
    args.milk = [ "steamed" ]
}

Case with value coercion

Since argvex returns all values as strings, you'll often want to convert them to the appropriate types.

import argvex from 'argvex'

const args = argvex()

if (args.temperature) {
    args.temperature = args.temperature.map(temperature => parseInt(temperature, 10))
}

Case with error handling

Wrap argvex calls in try-catch to handle parsing errors gracefully.

import argvex, { ArgvexError } from 'argvex'

try {
    const args = argvex({ strict: true })
    // todo: process args here
} catch (error) {
    if (error instanceof ArgvexError) {
        console.error('Invalid command line arguments')
        process.exit(1)
    }
    throw error
}