How to use specific website in regex

Question

I want the regex pattern to only match a9.com or www.a9.com
I have tried add ? before www. /?([www]+\.)+[\ba9\.com\b]/; but it shows error..
Did I miss anything ?

hope this result

a9.com   true
www.a9.com  true
a91.com  false
www.a91.com   false

https://jsfiddle.net/c2wsds0g/

var str = 'a9.com';

var regexPattern = /([www]+\.)+[\ba9\.com\b]/;
var result = regexPattern.test(str);
console.log(result)

only regex. not use split or other method

does that means group a pattern ?? http://stackoverflow.com/a/9801697/1775888 — user1775888, Oct 07 '16 at 21:09
It means [character set](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp#character-sets). — PM 77-1, Oct 07 '16 at 21:13
You got it. Also if you want `1 or 0` times, then `?` goes **after** a pattern. — PM 77-1, Oct 07 '16 at 21:17

ncardeli · Accepted Answer · 2016-10-07T21:18:32.203

2

This Regex sould do the trick:

(www\.)?a9\.com

The ´?´ quantifier, to make the group optional goes after the group, not before.

Bonus: I always test my regex with regexpal.com, you should try it. You´ll find a handy cheat sheet there too.

edited Oct 07 '16 at 21:18

answered Oct 07 '16 at 21:13

ncardeli

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should I add \b in before and after to avoid .comm or wwww – user1775888 Oct 07 '16 at 21:22
`/\b(www\.)?\ba9\.com\b/;` – user1775888 Oct 07 '16 at 21:25
1

Yes, you can use word boundaries, like this: \b(www\.)?a9\.com\b – ncardeli Oct 07 '16 at 21:27
You should have posted that requirement in the original question. Anyway, this should work: \b((www\.|[^\.])a9\.com\b) – ncardeli Oct 07 '16 at 22:46

How to use specific website in regex

1 Answers1