noControlCharactersInRegex (since vnext)

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

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.

Source: https://eslint.org/docs/latest/rules/no-control-regex

Examples

Invalid

jsx

 var pattern1 = /\x00/;

jsx

 var pattern2 = /\x0C/;

jsx

 var pattern3 = /\x1F/;

jsx

 var pattern4 = /\u000C/;

<pre class="language-text"><code class="language-text">nursery/noControlCharactersInRegex.js:1:17 <a href="https://docs.rome.tools/lint/rules/noControlCharactersInRegex">lint/nursery/noControlCharactersInRegex</a> ━━━━━━━━━━━━━━━━━ ✖ Unexpected control character(s) in regular expression: \u000C > 1 │ var pattern4 = /\u000C/; │ ^^^^^^^^ 2 │ ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed. </code></pre>

jsx

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

<pre class="language-text"><code class="language-text">nursery/noControlCharactersInRegex.js:1:17 <a href="https://docs.rome.tools/lint/rules/noControlCharactersInRegex">lint/nursery/noControlCharactersInRegex</a> ━━━━━━━━━━━━━━━━━ ✖ Unexpected control character(s) in regular expression: \u{C} > 1 │ var pattern5 = /\u{C}/u; │ ^^^^^^^^ 2 │ ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed. </code></pre>

jsx

 var pattern7 = new RegExp("\x0C");

<pre class="language-text"><code class="language-text">nursery/noControlCharactersInRegex.js:1:17 <a href="https://docs.rome.tools/lint/rules/noControlCharactersInRegex">lint/nursery/noControlCharactersInRegex</a> ━━━━━━━━━━━━━━━━━ ✖ Unexpected control character(s) in regular expression: \x0C > 1 │ var pattern7 = new RegExp("\x0C"); │ ^^^^^^^^^^^^^^^^^^ 2 │ ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed. </code></pre>

jsx

 var pattern7 = new RegExp("\\x0C");

<pre class="language-text"><code class="language-text">nursery/noControlCharactersInRegex.js:1:17 <a href="https://docs.rome.tools/lint/rules/noControlCharactersInRegex">lint/nursery/noControlCharactersInRegex</a> ━━━━━━━━━━━━━━━━━ ✖ Unexpected control character(s) in regular expression: \x0C > 1 │ var pattern7 = new RegExp("\\x0C"); │ ^^^^^^^^^^^^^^^^^^^ 2 │ ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed. </code></pre>

Valid

jsx

var pattern1 = /\x20/;
var pattern2 = /\u0020/;
var pattern3 = /\u{20}/u;
var pattern4 = /\t/;
var pattern5 = /\n/;
var pattern6 = new RegExp("\x20");

Lint Rule noControlCharactersInRegex

noControlCharactersInRegex (since vnext)

Examples

Invalid

Valid

Related links