Regex produces different result in javascript

Question

Why does this regex return an entirely different result in javascript as compared to an on-line regex tester, found at http://www.gskinner.com/RegExr/

var patt = new RegExp(/\D([0-9]*)/g);
"/144444455".match(patt);

The return in the console is:

["/144444455"]

While it does return the correct group in the regexr tester.

All I'm trying to do is extract the first amount inside a piece of text. Regardless if that text starts with a "/" or has a bunch of other useless information.

Regular expressions engines are not all the same, the built-in regex libraries vary by language. That online one uses the ActionScript 3 built-in library, as it is written in Flex/Flash. That is not the same as the one used by Javascript. — Orbling
– Orbling, Commented Sep 20, 2012 at 14:43

Tim Pietzcker · Accepted Answer · 2012-09-20 14:45:09Z

3

The regex does exactly what you tell it to:

\D matches a non-digit (in this case /)
[0-9]* matches a string of digits (144444455)

You will need to access the content of the first capturing group:

var match = patt.exec(subject);
if (match != null) {
    result = match[1];
}

Or simply drop the \D entirely - I'm not sure why you think you need it in the first place...

Then, you should probably remove the /g modifier if you only want to match the first number, not all numbers in your text. So,

result = subject.match(/\d+/);

should work just as well.

answered Sep 20, 2012 at 14:45

Tim Pietzcker

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1 Comment

Henrik Ammer Over a year ago

You beat me to it, was just about to answer. :)

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