> For AI agents: the complete documentation index is available at https://rslint.rs/llms.txt, the full documentation bundle is available at https://rslint.rs/llms-full.txt.

# no-dupe-args

[Added in v0.2.2](https://github.com/web-infra-dev/rslint/releases/tag/v0.2.2)
## Configuration

| Preset                   | Configured Value |
| ------------------------ | ---------------- |
| ✅ js.configs.recommended | `"error"`        |


```ts title=rslint.config.ts
import { defineConfig, js } from '@rslint/core';

export default defineConfig([
  js.configs.recommended,
  {
    rules: {
      'no-dupe-args': 'error',
    },
  },
]);
```

## Rule Details

Disallow duplicate arguments in `function` definitions. If more than one parameter has the same name in a function definition, the last occurrence "shadows" the preceding ones.

Examples of **incorrect** code for this rule:

```javascript
function foo(a, b, a) {
  console.log(a);
}

var bar = function (a, b, a) {};
```

Examples of **correct** code for this rule:

```javascript
function foo(a, b, c) {
  console.log(a, b, c);
}

var bar = function (a, b, c) {};
```

## Differences from ESLint

When a parameter name appears more than twice (e.g., `function foo(a, a, a)`), rslint reports an error on **each** duplicate occurrence (2 errors), while ESLint reports only once per duplicated name (1 error). This provides more precise diagnostic locations.

## Original Documentation

- [ESLint: no-dupe-args](https://eslint.org/docs/latest/rules/no-dupe-args)
- [Source code](https://github.com/eslint/eslint/blob/v10.8.1/lib/rules/no-dupe-args.js)