Parameters

Parameters (aka positional arguments) are the named slots that map onto argument values passed to the script — think of parameters as variable names and arguments as the values bound to them.

Arguments vs. parameters

Every non-flag value is an argument, available on the _ array:

const argv = cli({/* ... */});

// $ my-script file-a.txt file-b.txt
argv._; // => ["file-a.txt", "file-b.txt"] (string[])

Defining parameters gives those arguments names, enables validation, and improves the generated help. Names are accessed in camelCase on argv._.

Parameter formats

Declare parameters as strings using these markers:

Two ordering rules cleye enforces:

• Required parameters cannot come after optional parameters.
• A spread parameter must be last.

const argv = cli({
  parameters: [
    "<required parameter>",
    "[optional parameter]",
    "[optional spread...]",
  ],
});

// $ my-script a b c d
argv._.requiredParameter; // => "a"            (string)
argv._.optionalParameter; // => "b"            (string | undefined)
argv._.optionalSpread; // => ["c", "d"]     (string[])

The multi-word names in the markers (<first name>) are converted to camelCase keys (argv._.firstName).

End-of-flags (--)

A bare -- ends flag parsing: everything after it is treated as plain arguments, even if it looks like a flag. This mirrors npm run <script> -- <script args>.

All end-of-flag arguments are available on argv._['--']:

const argv = cli({/* ... */});

// $ my-script --my-flag -- --not-a-flag
argv._["--"]; // => ["--not-a-flag"]

You can also name the end-of-flags arguments by placing -- in the parameters array:

const argv = cli({
  name: "npm-run",
  parameters: ["<script>", "--", "[arguments...]"],
});

// $ npm-run echo -- hello world
argv._.script; // => "echo"            (string)
argv._.arguments; // => ["hello", "world"] (string[])

Validation

cleye validates the shape of arguments against the declared parameters (required present, ordering, spread). For value-level validation (e.g. "must be an existing file"), validate in your code after parsing, or push validation into a flag/parameter type function that throws — see flags.md and formats.md.