# InvalidArgumentError

**Kind:** Class

**Source:** [`lib/error.js`](https://github.com/tj/commander.js/blob/main/lib/error.js#L25)

InvalidArgumentError class

`InvalidArgumentError` represents an error raised when a caller passes an argument that does not meet an API's expected requirements. It lets validation code communicate argument-related failures distinctly from other error types.

**Extends:** `CommanderError`

## Diagram

```mermaid
graph LR
  A[Caller input] --> B[Argument validation]
  B -->|Invalid argument| C[InvalidArgumentError]
  C --> D[Caller handles error]
```

## Usage

```js
import { InvalidArgumentError } from './lib/error.js';

function setTimeoutDelay(delay) {
  if (typeof delay !== 'number' || delay < 0) {
    throw new InvalidArgumentError('delay must be a non-negative number');
  }

  return delay;
}

try {
  setTimeoutDelay(-1);
} catch (error) {
  if (error instanceof InvalidArgumentError) {
    console.error(error.message);
  } else {
    throw error;
  }
}
```

## AI Coding Instructions

- Throw `InvalidArgumentError` when validation fails because of an invalid caller-supplied argument.
- Include an error message that identifies the invalid argument and the expected constraint.
- Check for this class with `instanceof InvalidArgumentError` when callers need argument-specific handling.
- Keep argument validation close to the public API boundary before processing the input.

## Used by

3 references from 3 files. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

### Imported by (3)

- `program` — `index.js`:7
- `Argument` — `lib/argument.js`:3
- `Option` — `lib/option.js`:3