How to properly escape characters in regexp

问题

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

The problem occurs when this needle string contains special regex characters like *,+ and so on. It fails with error invalid quantifier.

I have browsed the web and found out that string can be escaped with \Q some string \E.

However, this does not always produce the desired behavior. For example:

var sNeedle = '*Stars!*';
var sMySTR = 'The contents of this string have no importance';
sMySTR.search('\Q' + sNeedle + '\E');

Result is -1. OK.

var sNeedle = '**Stars!**';
var sMySTR = 'The contents of this string have no importance';
sMySTR.search('\Q' + sNeedle + '\E');

Result is "invalid quantifier". This happens because 2 or more special characters are 'touching' each other, because:

var sNeedle = '*Dont touch me*Stars!*Dont touch me*';
var sMySTR = 'The contents of this string have no importance';
sMySTR.search('\Q' + sNeedle + '\E');

Will work OK.

I know I could make a function escapeAllBadChars(sInStr) and just add double slashes before every possible special regex character, but I'm wondering if there is a simpler way to do it?

回答1:

\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.

回答2:

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
}

回答3:

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.

回答4:

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, "\\$&");
}

来源：https://stackoverflow.com/questions/5663987/how-to-properly-escape-characters-in-regexp

标签

javascript

regex

escaping