Glossary

• name — The full name of the parameter (without spaces), for example, "anything", and it would be passed as an argument with two leading dashes like --anything.
• alias — The short form of the parameter, preferably one letter, for example, "a", and it would be passed as an argument with one leading dash like -a.

Basic Usage

• The arguments that are being passed to our application usually starts at index 2.
• We can use the spread operator to take the remaining arguments from process.argv.

const [_ignore0, _ignore1, ...rawParameters] = process.argv
const parameters = new ParameterParser(rawParameters)

getOne

• Gets just one parameter.

CLI input

someCommand --anything foo -x abc

or:

someCommand -a foo -x abc

To read the parameters

const parameters = new ParameterCollection(rawParameters)
const anything = parameters.getOne('a', 'anything')
console.log(anything) // foo

getBoolean

• Gets just one parameter and parse it as a boolean.
• Syntaxes that evaluate to true are -a, -a true, -a t, -a yes, -a y, -a 1, given that -a is the alias of the parameter.

CLI input

someCommand --anything

To read the parameters

const parameters = new ParameterCollection(rawParameters)
const input = parameters.getBoolean('a', 'anything')
console.log(input) // true

getArray

• Gets all parameters with the same name or alias.

CLI input

someCommand -a foo bar --anything baz -b abc -a qux

To read the parameters

const parameters = new ParameterCollection(rawParameters)
const inputs = parameters.getArray('a', 'anything')
console.log(inputs) // ['foo', 'bar', 'baz', 'qux']

getTrailing

• Finds the matching name OR alias, then get all values that are behind it, assuming that there will be no other parameters already.
• This is only used to enforce syntax style, prefer getArray whenever possible for more flexibility.

CLI input

someCommand -x aaa -y bbb -z ccc -a foo bar baz

To read the parameters

const parameters = new ParameterCollection(rawParameters)
const inputs = parameters.getTrailing('a', 'anything')
console.log(inputs) // ['foo', 'bar', 'baz']

getRemaining

• Gets all the parameter names, aliases, and values that are not being processed by the "get" methods mentioned above.
• Used to check and warn users about stray/unrecognized parameters that they may have provided.
• This should only be called after retrieving all necessary parameters.

someCommand -a foo -b bar

const parameters = new ParameterCollection(rawParameters)
const anything = parameters.getOne('a', 'anything')
const strayParameters = parameters.getRemaining()
console.log(strayParameters) // ['-b', 'bar']