# prefer-regex-literals

> Require regular expression literals instead of `RegExp()` with a fixed pattern

In `new RegExp("\\d+")` you write every backslash twice. Forget one and the pattern changes without an error, because `"\d+"` is the string `d+`. In the literal `/\d+/` you write the pattern as is, and a mistake in it is a syntax error, not an exception when that line runs.

A call is reported if the pattern and the flags are fixed strings: a string literal, a template literal without `${}`, or `String.raw` without `${}`. A pattern that's built at run time needs the constructor, so it isn't reported.

The report comes with a suggestion that replaces the call with the literal.

{/* Generated by src/codegen/lint-rule-docs.ts. Do not edit this section. */}

## Configure

Off by default. To turn it on:

```toml bunfig.toml
[lint.rules]
"prefer-regex-literals" = "error" # or "warn"
```

Every option, set to its default:

```toml bunfig.toml
[lint.rules]
"prefer-regex-literals" = ["error", {
  disallowRedundantWrapping = false,
}]
```

{/* End of the generated section. */}

## Examples

Reported:

{/* bad {"count": 3} */}
```js
const digits = new RegExp("\\d+");
const word = RegExp("hello", "gi");
const path = new RegExp(String.raw`\.tsx?$`);
```

Not reported:

{/* good */}
```js
const digits = /\d+/;
const word = /hello/gi;
const path = /\.tsx?$/;

const search = new RegExp(escape(query), "i");
const prefix = new RegExp(`^${name}:`);
```

## Options

| Option | Default | What it does |
| --- | --- | --- |
| `disallowRedundantWrapping` | `false` | Also report a regular expression literal passed to `RegExp`, alone or with fixed flags. |

{/* bad {"options": [{"disallowRedundantWrapping": true}], "count": 2} */}
```js
const digits = new RegExp(/\d+/);
const word = new RegExp(/hello/, "gi");
```

{/* good {"options": [{"disallowRedundantWrapping": true}]} */}
```js
const digits = /\d+/;
const word = /hello/gi;
const custom = new RegExp(/hello/, flags);
```