JavaScript Regex: Escape the string "c++"?

Question

I'm working on some regex for a input text field and have had some trouble escaping special characters such as "+" or "?".

I've used these two questions for doing so and they work for a string such as c+ but if I enter c++ I get following error in the console Invalid regular expression: /c++/: Nothing to repeat

Here's the code:

$('input').keyup(function(){
   var val = $(this).val().trim().toLowerCase();
    // from: https://stackoverflow.com/questions/3561493/is-there-a-regexp-escape-function-in-javascript
    //val.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&');

    //from: https://stackoverflow.com/questions/3446170/escape-string-for-use-in-javascript-regex
    val = val.replace(/[\-\[\]{}()*+?.,\\\^$|#\s]/g, "\\$&");

    var re = new RegExp(val, 'ig');
    console.log(re);
});

Here is a jsFiddle example of the issue

Thanks

Denys Séguret · Accepted Answer · 2015-06-23T07:59:33.067

1

There's a bug in your code. As a string is immutable in JavaScript, replace doesn't change it but returns a new one. You do the replacement but you doesn't take the returned value

Change

val.replace(/[\-\[\]{}()*+?.,\\\^$|#\s]/g, "\\$&");

to

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

Demonstration

edited Jun 23 '15 at 07:59

answered Jun 23 '15 at 07:50

Denys Séguret

355,860
83
755
726

Oh yes of cause, I feel so silly. Thank you so much :-) – Emil Devantie Brockdorff Jun 23 '15 at 11:12

score 1 · Answer 2 · answered Jun 23 '15 at 07:54

1

Your regex was fine, you just threw away the result of the replace call. Replace with val = val.replace(...);

Working fiddle

answered Jun 23 '15 at 07:54

Amit

43,881
8
73
106

Thank you so much - it was so easy :-) – Emil Devantie Brockdorff Jun 23 '15 at 11:12

JavaScript Regex: Escape the string "c++"?

2 Answers2