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noControlCharactersInRegex (since v1.0.0)

Diagnostic Category: lint/suspicious/noControlCharactersInRegex

Sources:

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.

Examples

Section titled Examples

Invalid

Section titled Invalid
 var pattern1 = /\x00/;
code-block.js:1:17 lint/suspicious/noControlCharactersInRegex ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected control character(s) in regular expression: \x00
  
  > 1 │  var pattern1 = /\x00/;
      │                 ^^^^^^
    2 │ 
  
  ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed.
  

 var pattern2 = /\x0C/;
code-block.js:1:17 lint/suspicious/noControlCharactersInRegex ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected control character(s) in regular expression: \x0C
  
  > 1 │  var pattern2 = /\x0C/;
      │                 ^^^^^^
    2 │ 
  
  ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed.
  

 var pattern3 = /\x1F/;
code-block.js:1:17 lint/suspicious/noControlCharactersInRegex ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected control character(s) in regular expression: \x1F
  
  > 1 │  var pattern3 = /\x1F/;
      │                 ^^^^^^
    2 │ 
  
  ℹ Control characters are unusual and potentially incorrect inputs, so they are disallowed.
  

 var pattern4 = /\u000C/;
code-block.js:1:17 lint/suspicious/noControlCharactersInRegex ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ 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.
  

 var pattern5 = /\u{C}/u;
code-block.js:1:17 lint/suspicious/noControlCharactersInRegex ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ 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.
  

 var pattern7 = new RegExp("\x0C");
code-block.js:1:17 lint/suspicious/noControlCharactersInRegex ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ 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.
  

 var pattern7 = new RegExp("\\x0C");
code-block.js:1:17 lint/suspicious/noControlCharactersInRegex ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ 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.

Valid

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