---
url: /docs/guide/usage/linter/rules/eslint/no-invalid-regexp.md
---

### What it does

Disallow invalid regular expression strings in RegExp constructors.

### Why is this bad?

An invalid pattern in a regular expression literal is a SyntaxError when the code is parsed,
but an invalid string in RegExp constructors throws a SyntaxError only when the code is executed.

### Examples

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

```js
RegExp("[");
RegExp(".", "z");
new RegExp("\\");
```

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

```js
RegExp(".");
new RegExp();
this.RegExp("[");
```

## Configuration

This rule accepts a configuration object with the following properties:

### allowConstructorFlags

type: `string[]`

default: `[]`

Case-sensitive array of flags that will be allowed.

## How to use

## Version

This rule was added in v0.9.4.

## References