Can someone explain the following regular expression for me?

Question

I got the following regular expression from config.js file in MEAN.JS framework

var urlRegex = new RegExp('^(?:[a-z]+:)?\/\/', 'i');

But I can't understand the regular expression. Can someone explain it or give me some matching examples?

Mostly I'm confused by `?:`. I find some explanation [here](http://stackoverflow.com/questions/3512471/non-capturing-group) — eeandrew, Oct 15 '14 at 12:43

score 1 · Accepted Answer · answered Oct 15 '14 at 12:22

1

^(?:[a-z]+:)?\/\/

Says from start there can be strings followed by:followd by//. strings is optional.Look at the demo.

asdsadas:// ===>will match

// ====>will match

213123dasdsad:// ====>will not match at the start is from number

answered Oct 15 '14 at 12:22

vks

Could you tell me the differences between `^(?:[a-z]+:)?\/\/` and `^([a-z]+:)?\/\/` ? – eeandrew Oct 15 '14 at 12:34
I find it. Check [here](http://stackoverflow.com/questions/3512471/non-capturing-group) – eeandrew Oct 15 '14 at 12:41
@user2878435 `?:` mean the group will not captured.later you can match it as `.group(1)` or `\1` or `$1`. – vks Oct 15 '14 at 13:06

1 Answers1