parsedArgs._ contains all the arguments that didn't have an option associated
with them.
Numeric-looking arguments will be returned as numbers unless options.string or
options.boolean is set for that argument name.
Any arguments after '--' will not be parsed and will end up in parsedArgs._.
options can be:
options.string - a string or array of strings argument names to always treat
as strings.
options.boolean - a boolean, string or array of strings to always treat as
booleans. if true will treat all double hyphenated arguments without equal
signs as boolean (e.g. affects --foo, not -f or --foo=bar). All
boolean arguments will be set to false by default.
options.collect - a string or array of strings argument names to always
treat as arrays. Collectable options can be used multiple times. All values
will be collected into an array. If a non collectable option is used multiple
times, the last value is used. All Collectable arguments will be set to []
by default.
options.negatable - a string or array of strings argument names which can be
negated by prefixing them with --no-, like --no-config.
options.alias - an object mapping string names to strings or arrays of
string argument names to use as aliases.
options.default - an object mapping string argument names to default values.
options.stopEarly - when true, populate parsedArgs._ with everything after
the first non-option.
options['--'] - when true, populate parsedArgs._ with everything before
the -- and parsedArgs['--'] with everything after the --. Here's an
example:
options.unknown - a function which is invoked with a command line parameter
not defined in the options configuration object. If the function returns
false, the unknown option is not added to parsedArgs.
By default, the flags module tries to determine the type of all arguments
automatically and the return type of the parse method will have an index
signature with any as value ({ [x: string]: any }).
If the string, boolean or collect option is set, the return value of the
parse method will be fully typed and the index signature of the return type
will change to { [x: string]: unknown }.