CODEWITHSUNDEEP
javascriptregex
Mostafa Talebi
Mostafa Talebi

Reputation: 9183

My regex works in online editor but in FireBug it makes the browser to crash

I have written the following regex to catch anything within two parenthesis of a text:

var rule = /[a-zA-Z0-9]*(\(+[a-zA-Z\s0-9]*\))*[a-zA-Z0-9\s]/;

It works in this website: http://regex101.com/ (javascript section)

Look the right side of the window and you see the bottom section shows the matched string which is what I want.

But in firebug when I execute the following code it crashes. Why? how then should I catch the group in parenthesis?

var rule = /^[a-zA-Z0-9\s]*(\(+[a-zA-Z\s0-9]*\))*[a-zA-Z0-9\s\,]*/;

var str = "He left us (with anger), but came back all cool and modest.";

var res = "";

while((res = rule.exec(str)) !== null)
{
   console.log("Good");
}

console.log(res);

Or maybe I'm totally wrong and am missing something?

Upvotes: 0

Views: 72

Answers (1)

cookie monster
cookie monster

Reputation: 10982

"But in firebug when I execute the following code it crashes. Why?"

To use .exec() in a loop like that, the regex must be global. Otherwise it's just going to keep getting the first match, resulting in an infinite loop.

// make it global ------------------------------------------------v
var rule = /^[a-zA-Z0-9\s]*(\(+[a-zA-Z\s0-9]*\))*[a-zA-Z0-9\s\,]*/g;

When global, the regex object becomes stateful, and each subsequent .exec() will begin from the character after the last match.

When there are finally no matches left, it'll return null, breaking the loop.

As others pointed out in the comments, the leading ^ will guarantee only one match (without the m modifier anyway), so you'll probably want to remove that. It's not the cause of the crash though.

Upvotes: 3

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