> 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.

# prefer-as-const

[Added in v0.1.4](https://github.com/web-infra-dev/rslint/releases/tag/v0.1.4)
## Configuration

| Preset                              | Configured Value |
| ----------------------------------- | ---------------- |
| ✅ ts.configs.recommended            | `"error"`        |
| ✅ ts.configs.recommendedTypeChecked | `"error"`        |
| ✅ ts.configs.strict                 | `"error"`        |
| ✅ ts.configs.strictTypeChecked      | `"error"`        |


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

export default defineConfig([
  ts.configs.recommended,
  {
    rules: {
      '@typescript-eslint/prefer-as-const': 'error',
    },
  },
]);
```

## Rule Details

Enforce the use of `as const` over literal type assertions. Using `as const` is preferred because it more clearly expresses intent, consistently applies to all literal values, and enables deeper immutability for objects and arrays.

This rule flags type assertions (`as` or angle-bracket style) and type annotations on variable or property declarations where the asserted/annotated type is a literal type that matches the literal value.

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

```typescript
let foo = 'bar' as 'bar';
let baz = 1 as 1;
let qux = <'bar'>'bar';
let x: 10 = 10;
```

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

```typescript
let foo = 'bar' as const;
let baz = 1 as const;
let arr = [1, 2, 3] as const;
```

## Original Documentation

- [typescript-eslint: prefer-as-const](https://typescript-eslint.io/rules/prefer-as-const)
- [Source code](https://github.com/typescript-eslint/typescript-eslint/blob/v8.67.0/packages/eslint-plugin/src/rules/prefer-as-const.ts)