mri

Quickly scan for CLI flags and arguments

This is a fast and lightweight alternative to minimist and yargs-parser.

It only exists because I find that I usually don't need most of what minimist and yargs-parser have to offer. However, mri is similar enough that it might function as a "drop-in replacement" for you, too!

See Comparisons for more info.

Install

$ npm install --save mri

Usage

$ demo-cli --foo --bar=baz -mtv -- hello world

const mri = require('mri');

const argv = process.argv.slice(2);

mri(argv);
//=> { _: ['hello', 'world'], foo:true, bar:'baz', m:true, t:true, v:true }

mri(argv, { boolean:['bar'] });
//=> { _: ['baz', 'hello', 'world'], foo:true, bar:true, m:true, t:true, v:true }

mri(argv, {
  alias: {
    b: 'bar',
    foo: ['f', 'fuz']
  }
});
//=> { _: ['hello', 'world'], foo:true, f:true, fuz:true, b:'baz', bar:'baz', m:true, t:true, v:true }

API

mri(args, options)

Return: Object

args

Type: Array
Default: []

An array of arguments to parse. For CLI usage, send process.argv.slice(2). See process.argv for info.

options.alias

Type: Object
Default: {}

An object of keys whose values are Strings or Array<String> of aliases. These will be added to the parsed output with matching values.

options.boolean

Type: Array|String
Default: []

A single key (or array of keys) that should be parsed as Booleans.

options.default

Type: Object
Default: {}

An key:value object of defaults. If a default is provided for a key, its type (typeof) will be used to cast parsed arguments.

mri(['--foo', 'bar']);
//=> { _:[], foo:'bar' }

mri(['--foo', 'bar'], {
  default: { foo:true, baz:'hello', bat:42 }
});
//=> { _:['bar'], foo:true, baz:'hello', bat:42 }

Note: Because --foo has a default of true, its output is cast to a Boolean. This means that foo=true, making 'bar' an extra argument (_ key).

options.string

Type: Array|String
Default: []

A single key (or array of keys) that should be parsed as Strings.

options.unknown

Type: Function
Default: undefined

Callback that is run when a parsed flag has not been defined as a known key or alias. Its only parameter is the unknown flag itself; eg --foobar or -f.

Once an unknown flag is encountered, parsing will terminate, regardless of your return value.

Note: mri only checks for unknown flags if options.unknown and options.alias are populated. Otherwise, everything will be accepted.

Comparisons

minimist

mri is 5x faster (see benchmarks)
Numerical values are cast as Numbers when possible
- A key (and its aliases) will always honor opts.boolean or opts.string

Short flag groups are treated as Booleans by default:

minimist(['-abc', 'hello']);
//=> { _:[], a:'', b:'', c:'hello' }

mri(['-abc', 'hello']);
//=> { _:[], a:true, b:true, c:'hello' }

The opts.unknown behaves differently:
- Unlike minimist, mri will not continue continue parsing after encountering an unknown flag
Missing options:
- opts.stopEarly
- opts['--']
Ignores newlines (\n) within args (see test)
Ignores slashBreaks within args (see test)
Ignores dot-nested flags (see test)

yargs-parser

mri is 40x faster (see benchmarks)
Numerical values are cast as Numbers when possible
- A key (and its aliases) will always honor opts.boolean or opts.string
Missing options:
- opts.array
- opts.config
- opts.coerce
- opts.count
- opts.envPrefix
- opts.narg
- opts.normalize
- opts.configuration
- opts.number
- opts['--']
Missing parser.detailed() method
No additional configuration object
Added options.unknown feature

Benchmarks

Running Node.js v10.13.0

Load Times:
  nopt          3.179ms
  yargs-parser  2.137ms
  minimist      0.746ms
  mri           0.517ms

Benchmark:
  minimist      x    328,747 ops/sec ±1.09% (89 runs sampled)
  mri           x  1,622,801 ops/sec ±0.94% (92 runs sampled)
  nopt          x    888,223 ops/sec ±0.22% (92 runs sampled)
  yargs-parser  x     30,538 ops/sec ±0.81% (91 runs sampled)

mri