Simple argument parsing function for Node.js

README.md

Usage

const args = parseArgs(process.argv.splice(2))

const args = parseArgs(['--foo', 'one'])

console.log(args.foo) // ['one']

const args = parseArgs(['--foo', 'one', '--fizz', '--buzz', '--foo', 'two'])

console.log(args.foo) // ['one', 'two']
console.log(args.fizz) // ['true']
console.log(args.buzz) // ['true']

const args = parseArgs(['--foo', '--bar', 'one', 'fizzbuzz'])

console.log(args.foo) // ['true']
console.log(args.bar) // ['one']
console.log(args._) // ['fizzbuzz']

TypeScript

const args = parseArgs<['foo', 'bar']>(process.argv.splice(2))

args.foo // fine
args.bar // fine
args.fizz // type error

parse-args.js

/**
 * @param {Array.<string>} argsList
 * @returns {Object.<string,string[]>}
 */
export function parseArgs(argsList) {
    const args = {
        _: []
    }
    
    for (let i = 0; i < argsList.length; i++) {
        const completeSymbol = argsList[i]
        const strippedSymbol = completeSymbol.replace('-', '').replace('-', '')

        if (completeSymbol.startsWith('-')) {
            if (!(strippedSymbol in args)) {
                args[strippedSymbol] = []
            }
            const nextSymbol = argsList[i+1]
            if (nextSymbol === undefined || nextSymbol.startsWith('-')) {
                args[strippedSymbol].push(true)
            } else {
                args[strippedSymbol].push(nextSymbol)
                i++
            }
            continue
        }

        args._.push(strippedSymbol)
    }
    
    return args
}

parse-args.ts

export type ParsedArgs<T extends Array<string>> = {
    [K in T[number]]: string[]
}

export function parseArgs(argsList: string[]): ParsedArgs<['_']> & { [key: string]: string[] | undefined }
export function parseArgs<T extends Array<string>>(argsList: string[]): ParsedArgs<['_']> & ParsedArgs<T>
export function parseArgs<T extends Array<string>>(argsList: string[]): ParsedArgs<['_']> & ParsedArgs<T> {
    const args: ParsedArgs<['_']> = {
        _: []
    }
    
    for (let i = 0; i < argsList.length; i++) {
        const completeSymbol = argsList[i]
        const strippedSymbol = completeSymbol.replace('-', '').replace('-', '')

        if (completeSymbol.startsWith('-')) {
            if (!(strippedSymbol in args)) {
                args[strippedSymbol] = []
            }
            const nextSymbol = argsList[i+1]
            if (nextSymbol === undefined || nextSymbol.startsWith('-')) {
                args[strippedSymbol].push(true)
            } else {
                args[strippedSymbol].push(nextSymbol)
                i++
            }
            continue
        }

        args._.push(strippedSymbol)
    }
    
    return args as ParsedArgs<['_']> & ParsedArgs<T>
}