When true, populate the result _ with everything before the -- and the result ['--'] with everything after the --.

An object mapping string names to strings or arrays of string argument names to use as aliases.

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.

An object mapping string argument names to default values.

When true, populate the result _ with everything after the first non-option.

A string or array of strings argument names to always treat as strings.

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 one array. If a non-collectable option is used multiple times, the last value is used. All Collectable arguments will be set to [] by default.

A string or array of strings argument names which can be negated by prefixing them with --no-, like --no-config.

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.