---
url: /docs/guide/usage/linter/rules/typescript/prefer-promise-reject-errors.md
---

### What it does

This rule enforces passing an Error object to `Promise.reject()`.

### Why is this bad?

It's considered good practice to only reject promises with Error objects. This is because Error objects automatically capture a stack trace, which is useful for debugging. Additionally, some tools and environments expect rejection reasons to be Error objects.

### Examples

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

```ts
Promise.reject("error"); // rejecting with string

Promise.reject(42); // rejecting with number

Promise.reject(true); // rejecting with boolean

Promise.reject({ message: "error" }); // rejecting with plain object

Promise.reject(null); // rejecting with null

Promise.reject(); // rejecting with undefined

const error = "Something went wrong";
Promise.reject(error); // rejecting with non-Error variable
```

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

```ts
Promise.reject(new Error("Something went wrong"));

Promise.reject(new TypeError("Invalid type"));

Promise.reject(new RangeError("Value out of range"));

// Custom Error subclasses
class CustomError extends Error {
  constructor(message: string) {
    super(message);
    this.name = "CustomError";
  }
}
Promise.reject(new CustomError("Custom error occurred"));

// Variables that are Error objects
const error = new Error("Error message");
Promise.reject(error);
```

## Configuration

This rule accepts a configuration object with the following properties:

### allow

type: `array`

default: `[]`

An array of type or value specifiers for additional types that are allowed
as Promise rejection reasons.

#### allow\[n]

type: `object | string`

Type or value specifier for matching specific declarations

Supports four types of specifiers:

1. **String specifier** (deprecated): Universal match by name

```json
"Promise"
```

2. **File specifier**: Match types/values declared in local files

```json
{ "from": "file", "name": "MyType" }
{ "from": "file", "name": ["Type1", "Type2"] }
{ "from": "file", "name": "MyType", "path": "./types.ts" }
```

3. **Lib specifier**: Match TypeScript built-in lib types

```json
{ "from": "lib", "name": "Promise" }
{ "from": "lib", "name": ["Promise", "PromiseLike"] }
```

4. **Package specifier**: Match types/values from npm packages

```json
{ "from": "package", "name": "Observable", "package": "rxjs" }
{ "from": "package", "name": ["Observable", "Subject"], "package": "rxjs" }
```

##### allow\[n].from

type: `"file"`

Must be "file"

##### allow\[n].name

type: `array | string`

The name(s) of the type or value to match

Name specifier that can be a single string or array of strings

###### allow\[n].name\[n]

type: `string`

##### allow\[n].path

type: `string`

Optional file path to specify where the types or values must be declared.
If omitted, all files will be matched.

### allowEmptyReject

type: `boolean`

default: `false`

Whether to allow calling `Promise.reject()` with no arguments.

### allowThrowingAny

type: `boolean`

default: `false`

Whether to allow rejecting Promises with values typed as `any`.

### allowThrowingUnknown

type: `boolean`

default: `false`

Whether to allow rejecting Promises with values typed as `unknown`.

## How to use

## Version

This rule was added in v1.12.0.

## References