Is there a RegExp escape function in JavaScript

Question

I just want to create a regular expression out of any possible string  var usersString    quot Hello     World     quot   var expression   new RegExp RegExp escape usersString   var matches    quot Hello quot  match expression    Is there a built-in method for that  If not  what do people use  Ruby has RegExp escape  I don t feel like I d need to write my own  there have got to be something standard out there

User · Answer

Nothing should prevent you from just escaping every non-alphanumeric character:

usersString.replace(/(?=\W)/g, '\\');

You lose a certain degree of readability when doing re.toString() but you win a great deal of simplicity (and security).

According to ECMA-262, on the one hand, regular expression "syntax characters" are always non-alphanumeric, such that the result is secure, and special escape sequences (\d, \w, \n) are always alphanumeric such that no false control escapes will be produced.

User · Answer

XRegExp has an escape function   XRegExp escape  Escaped   lt   gt        - gt   Escaped     lt    gt     More on  http   xregexp com api  escape

User · Answer

This is a shorter version   RegExp escape   function s        return s replace    -    -      g       amp         This includes the non-meta characters of     amp      and    but the JavaScript RegExp specification allows this

User · Answer

The functions in the other answers are overkill for escaping entire regular expressions  they may be useful for escaping parts of regular expressions that will later be concatenated into bigger regexps    If you escape an entire regexp and are done with it  quoting the metacharacters that are either standalone                          or start something           is all you need   String prototype regexEscape   function regexEscape       return this replace                 g       amp          And yes  it s disappointing that JavaScript doesn t have a function like this built-in

User · Answer

escapeRegExp   function str      if  str    null  return       return String str  replace                            g      1

User · Answer

Mozilla Developer Network s Guide to Regular Expressions provides this escaping function   function escapeRegExp string      return string replace                     g       amp          amp  means the whole matched string

User · Answer

There has only ever been and ever will be 12 meta characters that need to be escaped to be considered a literal  It doesn t matter what is done with the escaped string  inserted into a balanced regex wrapper or appended  It doesn t matter  Do a string replace using this var escaped string   oldstring replace                  g       amp

User · Answer

There is an ES7 proposal for RegExp escape at https   github com benjamingr RexExp escape   with a polyfill available at https   github com ljharb regexp escape  An example based on the rejected ES proposal  includes checks if the property already exists  in the case that TC39 backtracks on their decision   Code  if   Object prototype hasOwnProperty call RegExp   escape        RegExp escape   function string           https   developer mozilla org en-US docs Web JavaScript Guide Regular Expressions Escaping        https   github com benjamingr RegExp escape issues 37     return string replace       -               g       amp          amp  means the whole matched string         Code Minified  Object prototype hasOwnProperty call RegExp  quot escape quot     RegExp escape function e  return e replace       -               g  quot     amp  quot               var assert   require  assert      var str    hello  how are you    var regex   new RegExp RegExp escape str    g    assert equal String regex     hello   how are you   g      There is also an npm module at  https   www npmjs com package regexp escape  One can install this and use it as so   npm install regexp escape  or yarn add regexp escape   var escape   require  regexp escape    var assert   require  assert      var str    hello  how are you    var regex   new RegExp escape str    g    assert equal String regex     hello   how are you   g     In the GitHub  amp  amp  NPM page are descriptions of how to use the shim polyfill for this option  as well  That logic is based on return RegExp escape    implementation   where implementation contains the regexp used above   The NPM module is an extra dependency  but it also make it easier for an external contributor to identify logical parts added to the code

User · Answer

Another  much safer  approach is to escape all the characters  and not just a few special ones that we currently know  using the unicode escape format  u code    function escapeRegExp text        return Array from text              map char   gt     u   char charCodeAt 0  toString 16                  join         console log escapeRegExp  a b          u 61  u 2e  u 62     Please note that you need to pass the u flag for this method to work   var expression   new RegExp escapeRegExp usersString    u

User · Answer

In jQuery UI s autocomplete widget  version 1 9 1  they use a slightly different regular expression  line 6753   here s the regular expression combined with bobince s approach  RegExp escape   function  value          return value replace    -                     s  g   quot     amp  quot

User · Answer

The function linked above is insufficient  It fails to escape   or    start and end of string   or -  which in a character group is used for ranges  Use this function  function escapeRegex string        return string replace   -                    g       amp        While it may seem unnecessary at first glance  escaping -  as well as    makes the function suitable for escaping characters to be inserted into a character class as well as the body of the regex  Escaping   makes the function suitable for escaping characters to be used in a JavaScript regex literal for later evaluation  As there is no downside to escaping either of them  it makes sense to escape to cover wider use cases  And yes  it is a disappointing failing that this is not part of standard JavaScript

User · Answer

Most of the expressions here solve single specific use cases   That s okay  but I prefer an  always works  approach   function regExpEscape literal string        return literal string replace   -           lt              s   g       amp         This will  fully escape  a literal string for any of the following uses in regular expressions    Insertion in a regular expression  E g  new RegExp regExpEscape str   Insertion in a character class  E g  new RegExp       regExpEscape str         Insertion in integer count specifier  E g  new RegExp  x 1     regExpEscape str         Execution in non-JavaScript regular expression engines    Special Characters Covered    -  Creates a character range in a character class         Starts   ends a character class         Starts   ends a numeration specifier         Starts   ends a group             Specifies repetition type     Matches any character     Escapes characters  and starts entities     Specifies start of matching zone  and negates matching in a character class     Specifies end of matching zone     Specifies alternation     Specifies comment in free spacing mode   s  Ignored in free spacing mode     Separates values in numeration specifier     Starts or ends expression     Completes special group types  and part of Perl-style character classes     Negates zero-width group   lt       Part of zero-width group specifications    Notes      is not strictly necessary in any flavor of regular expression  However  it protects in case someone  shudder  does eval       pattern            ensures that if the string is meant to be an integer in the numerical specifier  it will properly cause a RegExp compiling error instead of silently compiling wrong     and  s do not need to be escaped in JavaScript  but do in many other flavors  They are escaped here in case the regular expression will later be passed to another program      If you also need to future-proof the regular expression against potential additions to the JavaScript regex engine capabilities  I recommend using the more paranoid   function regExpEscapeFuture literal string        return literal string replace    A-Za-z0-9   g       amp         This function escapes every character except those explicitly guaranteed not be used for syntax in future regular expression flavors     For the truly sanitation-keen  consider this edge case   var s       new RegExp   choice1 choice2     regExpEscape s            This should compile fine in JavaScript  but will not in some other flavors  If intending to pass to another flavor  the null case of s        should be independently checked  like so   var s       new RegExp   choice1 choice2     s         regExpEscape s

User · Answer

There is an ES7 proposal for RegExp escape at https   github com benjamingr RexExp escape   with a polyfill available at https   github com ljharb regexp escape

User · Answer

For anyone using Lodash  since v3 0 0 a   escapeRegExp function is built-in    escapeRegExp   lodash  https   lodash com              lodash    https     lodash  com       And  in the event that you don t want to require the full Lodash library  you may require just that function

User · Answer

Rather than only escaping characters which will cause issues in your regular expression  e g   a blacklist   consider using a whitelist instead  This way each character is considered tainted unless it matches  For this example  assume the following expression  RegExp escape  be      be     This whitelists letters  number and spaces  RegExp escape   function  string        return string replace      w d s   gi      1       Returns   quot be         be quot   This may escape characters which do not need to be escaped  but this doesn t hinder your expression  maybe some minor time penalties - but it s worth it for safety

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