How to properly escape characters in regexp

Question

I want to do a string search inside a string. Simply saying MySTR.search(Needle).

The problem occurs when this needle string contains speci

Answer 1

Duplicate of https://stackoverflow.com/a/6969486/151312

This is proper as per MDN (see explanation in post above):

function escapeRegExp(str) {
  return str.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&");
}

Answer 2

I performed a quick Google search to see what's out there and it appears that you've got a few options for escaping regular expression characters. According to one page, you can define & run a function like below to escape problematic characters:

RegExp.escape = function(text) {
    return text.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, "\\$&");
}

Alternatively, you can try and use a separate library such as XRegExp, which already handles nuances you're trying to re-solve.

Answer 3

\Q...\E doesn't work in JavaScript (at least, they don't escape anything...) as you can see:

var s = "*";
print(s.search(/\Q*\E/));
print(s.search(/\*/));

produces:

-1
0

as you can see on Ideone.

The following chars need to be escaped:

• (
• )
• [
• {
• *
• +
• .
• $
• ^
• \
• |
• ?

So, something like this would do:

function quote(regex) {
  return regex.replace(/([()[{*+.$^\\|?])/g, '\\$1');
}

No, ] and } don't need to be escaped: they have no special meaning, only their opening counter parts.

Note that when using a literal regex, /.../, you also need to escape the / char. However, / is not a regex meta character: when using it in a RegExp object, it doesn't need an escape.

Answer 4

I'm just dipping my feet in Javascript, but is there a reason you need to use the regex engine at all? How about

var sNeedle = '*Stars!*';
var sMySTR = 'The contents of this string have no importance';
if ( sMySTR.indexOf(sNeedle) > -1 ) {
   //found it
}