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# no-base-to-string

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

| Preset                              | Configured Value |
| ----------------------------------- | ---------------- |
| ✅ ts.configs.recommendedTypeChecked | `"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/no-base-to-string': 'error',
    },
  },
]);
```

## Rule Details

Require `.toString()` and `.toLocaleString()` to only be called on objects which provide useful information when stringified. JavaScript calls `toString()` implicitly in string contexts such as template literals and string concatenation. The default `Object.prototype.toString()` returns `"[object Object]"`, which is rarely useful.

This rule uses type information to detect when a value will use the base `Object.prototype.toString()` and flags string concatenation, template literals, explicit `.toString()`/`.toLocaleString()` calls, `String()` calls, and `.join()` on arrays containing such types.

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

```typescript
class MyClass {}
const obj = new MyClass();

`Value: ${obj}`;
'' + obj;
obj.toString();
[obj].join(',');
```

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

```typescript
`Value: ${'str'}`;
'' + 42;

class MyClass {
  toString() {
    return 'MyClass';
  }
}
`Value: ${new MyClass()}`;
```

## Original Documentation

- [typescript-eslint: no-base-to-string](https://typescript-eslint.io/rules/no-base-to-string)
- [Source code](https://github.com/typescript-eslint/typescript-eslint/blob/v8.28.0/packages/eslint-plugin/src/rules/no-base-to-string.ts)