command-line-parser

This statement:

const argsObj = require('command-line-parser')();

returns this argsObj object:

{
    v: true,
    debug: true,
    host: 'there.com',
    port: '8081',
    _args: [ 'myfile1', 'myfile2' ]
}

when invoked with:

node ./myscript.js myfile1 -v -debug -host there.com -port 8081 myfile2

This simple lightweight module exports a default function that takes an array of command-line arguments and returns a parsed object (a bit simpler than the venerable minimist or commander).

Arguments as keys and values

A key argument (starts with a dash) looks to the next argument for a value, such as -foo bar. If foo does not find a value, a default value of true will be set.

There's a few ways in which foo might not find a value:

• the following argument also starts with a dash, as in -foo -hey
• there are no more arguments
• foo is set in booleanKeys of config (an optional argument):

const argsObj = require('command-line-parser')({
    booleanKeys: [ 'foo' ]
});

A key with multiple leading dashes such as --debug will be the same as -debug (with the exception of overriding the optional argument allowKeyGrouping described below).

A key with embedded dashes or spaces will be converted to camelCase from camel-case.

Arguments that don't fulfill the role of a key or a value will be added in an array to a key called _args in the parsed object.

To avoid any arguments intended for _args from becoming the unintentional value of a preceding boolean key, either specify that boolean key in booleanKeys of config, or follow that boolean key with a placeholder argument such as a single - or double dash -- on the command line.

node ./myscript.js -d -- foo1 foo2 foo3

Embedding numerical values within keys

Instead of having to separate a numerical argument from its key:

node ./myscript.js -n 8

it may be embedded in the key:

node ./myscript.js -n8

by setting allowEmbeddedValues in the config:

const argsObj = require('command-line-parser')({
    allowEmbeddedValues: true
});

to give the result

{
    n: 8
}

Single letter key grouping

To parse a leading-dash argument such as -abc as single-letter keys instead of one multi-letter key, then set allowKeyGrouping in config so that

node ./myscript.js -abc

when parsed by

const argsObj = require('command-line-parser')({
    allowKeyGrouping: true
});

gives the result

{
    a: true,
    b: true,
    c: true
}

allowKeyGrouping can be overridden on the command-line by prefixing the argument with double-dashes, so that

node ./myscript.js --abc

becomes

{
    abc: true
}

Passing configuration

An optional configuration object may be passed in that will override these default values:

const argsObj = require('command-line-parser')({
    args = process.argv.slice(2),	// skip the binary and script file args
    booleanKeys = [],
    allowKeyGrouping: false,
    allowEmbeddedValues: false
});

Installation and testing

Install with npm install command-line-parser.

Test via npm test (and see test/index.js for some examples).

Useful destructuring assignment pattern

This is a common pattern using destructuring assignment (available in ES6 or via Babel) which can be useful here, especially with default values, and perhaps renaming _args:

const {
    v,
    debug = false,
    host = 'default.com',
    port = '80',
    _args: files = []
} = argsObj ;

will assign the locally scoped constant variables v, debug, host, port, and files.