javascript syntax error: invalid regular expression

Question

I am writing an application in javascript. In my application there is an option to search for a string/regex. The problem is match returns javascript error if user types wrong value. Sample code:

  function myFunction() {
      var filter = $("#text_id").val();
      var query = "select * from table";
      var found;
      if (query.match(filter) != -1) {
        found = true;
      } 
      else{
        found = false;
      }
       //Do something
    }

jsfiddle: http://jsfiddle.net/ZVNMq/

Enter the string: sel/\

Match returns js error - Uncaught SyntaxError: Invalid regular expression: /sel\/: \ at end of pattern.

Is there any way to check whether the string is valid regex or not?

heeding nhahtdh's advice would be a good idea in any case. in your specific situation you have to escape the escape symbol ``. generally speaking you should escape all characters having a special meaning in a regexp if you allow unvalidated user input of the pattern. if you just happen to store the data in dom nodes you'll probably get along without the extra effort. — collapsar
– collapsar, Commented Apr 23, 2013 at 11:51

Ja͢ck · Accepted Answer · 2014-04-01 12:46:11Z

29

In this case you didn't actually need regular expressions, but if you want to avoid invalid characters in your expression you should escape it:

RegExp.quote = function(str) {
     return str.replace(/([.?*+^$[\]\\(){}|-])/g, "\\$1");
};

Usage:

var re = new RegExp(RegExp.quote(filter));

Without a regular expression you could have done this:

if (query.indexOf(filter) != -1) {
}

edited Apr 1, 2014 at 12:46

answered Apr 23, 2013 at 11:55

Ja͢ck

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1 Comment

Greg Blass Over a year ago

I didn't need the regex in my case. Simple search. Thanks for pointing that out!

Bergi · Accepted Answer · 2013-04-23 11:47:48Z

15

Use a try-catch statement:

function myFunction() {
    var filter = $("#text_id").val();
    var query = "select * from table";
    try {
        var regex = new RegExp(filter);
    } catch(e) {
        alert(e);
        return false;
    }
    var found = regex.test(query);
}

answered Apr 23, 2013 at 11:47

Bergi

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Comments

Ivan Kharkivskyi · Accepted Answer · 2021-06-15 12:40:51Z

1

    RegExp.quote = function allowSpecialSymbols(str) {
      return str.replace(/([.?*+^$[\]\\(){}|-])/g, '');
    };
    const regExp = new RegExp(RegExp.quote('some \ string'), 'i');

Also, you can escape special characters.

edited Jun 15, 2021 at 12:40

answered Jun 15, 2021 at 12:28

Ivan Kharkivskyi

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1 Comment

coreuter Over a year ago

This answer doesn't seem to be much different from this already provided answer.

strakez · Accepted Answer · 2013-04-23 11:51:58Z

0

Perhaps you should try escaping the slashes on a line before the "var query". If you want to search a string for a slash in regex, it must be escaped or regex will read it as a reserved character.

answered Apr 23, 2013 at 11:51

strakez

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