noControlCharactersInRegex

import { Tabs, TabItem } from '@astrojs/starlight/components';

<Tabs> <TabItem label="JavaScript (and super languages)" icon="seti:javascript"> ## Summary - Rule available since: `v1.0.0` - Diagnostic Category: [`lint/suspicious/noControlCharactersInRegex`](/reference/diagnostics#diagnostic-category) - This rule is **recommended**, meaning it is enabled by default. - This rule doesn't have a fix. - The default severity of this rule is [**error**](/reference/diagnostics#error). - Sources: - Same as [`no-control-regex`](https://eslint.org/docs/latest/rules/no-control-regex)

How to configure

json

{
	"linter": {
		"rules": {
			"suspicious": {
				"noControlCharactersInRegex": "error"
			}
		}
	}
}

Description

Prevents from having control characters and some escape sequences that match control characters in regular expression literals.

Control characters are hidden special characters that are numbered from 0 to 31 in the ASCII system. They're not commonly used in JavaScript text. So, if you see them in a pattern (called a regular expression), it's probably a mistake.

The following elements of regular expression patterns are considered possible errors in typing and are therefore disallowed by this rule:

Hexadecimal character escapes from \x00 to \x1F
Unicode character escapes from \u0000 to \u001F
Unicode code point escapes from \u{0} to \u{1F}
Unescaped raw characters from U+0000 to U+001F

Control escapes such as \t and \n are allowed by this rule.

Examples

Invalid

 var pattern1 = /\x00/;

<pre class="language-text"><code class="language-text">code-block.js:1:18 <a href="https://biomejs.dev/linter/rules/no-control-characters-in-regex">lint/suspicious/noControlCharactersInRegex</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ✖ Unexpected control character in a regular expression. > 1 │ var pattern1 = /\x00/; │ ^^^^ 2 │ ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed. </code></pre>

 var pattern2 = /\x0C/;

<pre class="language-text"><code class="language-text">code-block.js:1:18 <a href="https://biomejs.dev/linter/rules/no-control-characters-in-regex">lint/suspicious/noControlCharactersInRegex</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ✖ Unexpected control character in a regular expression. > 1 │ var pattern2 = /\x0C/; │ ^^^^ 2 │ ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed. </code></pre>

 var pattern3 = /\x1F/;

<pre class="language-text"><code class="language-text">code-block.js:1:18 <a href="https://biomejs.dev/linter/rules/no-control-characters-in-regex">lint/suspicious/noControlCharactersInRegex</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ✖ Unexpected control character in a regular expression. > 1 │ var pattern3 = /\x1F/; │ ^^^^ 2 │ ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed. </code></pre>

 var pattern4 = /\u000C/;

<pre class="language-text"><code class="language-text">code-block.js:1:18 <a href="https://biomejs.dev/linter/rules/no-control-characters-in-regex">lint/suspicious/noControlCharactersInRegex</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ✖ Unexpected control character in a regular expression. > 1 │ var pattern4 = /\u000C/; │ ^^^^^^ 2 │ ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed. </code></pre>

 var pattern5 = /\u{C}/u;

<pre class="language-text"><code class="language-text">code-block.js:1:18 <a href="https://biomejs.dev/linter/rules/no-control-characters-in-regex">lint/suspicious/noControlCharactersInRegex</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ✖ Unexpected control character in a regular expression. > 1 │ var pattern5 = /\u{C}/u; │ ^^^^^ 2 │ ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed. </code></pre>

Valid

var pattern1 = /\x20/;
var pattern2 = /\u0020/;
var pattern3 = /\u{20}/u;
var pattern4 = /\t/;
var pattern5 = /\n/;

</TabItem> </Tabs>

How to configure

Description

Examples

Invalid

Valid

Related links