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# default-param-last

[Added in v0.1.14](https://github.com/web-infra-dev/rslint/releases/tag/v0.1.14)
## Configuration


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

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

## Rule Details

Enforce default parameters to be last. This is the TypeScript-enhanced version of the ESLint `default-param-last` rule. It also handles TypeScript-specific optional parameters (those with a `?` modifier), enforcing that they come after required parameters.

Putting default and optional parameters last makes function calls clearer, since callers do not need to pass `undefined` to skip optional arguments.

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

```typescript
function foo(a = 1, b: number) {}

function bar(a?: string, b: number) {}

class MyClass {
  method(a = 0, b: string) {}
}
```

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

```typescript
function foo(a: number, b = 1) {}

function bar(a: number, b?: string) {}

function baz(a: number, b = 1, ...rest: number[]) {}
```

## Original Documentation

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