Level4 again  Go to the Training: Regex challenge

/^wechall4?(?=\.(jpg|gif|tiff|bmp|png)$)/

Can you help me find why this regex is incorrect?
Are there any incorrect cases which can bypass it?

I've tested it and it captures only filename (with or without 4) and only with specified extension.

Thanks for help!

It doesn't capture filename, it matches filename and extension and additionally captures extension without the dot. You must to capture filename and only filename.

Edit.
Seems that you tested it wrong. ;)

what do you mean capture? what is the differenct between capture and matches?

i see two problems whith your regex:
- you have two groups. one should be enough...
- how do you start a non-capturing group? hint: it's not ?=

capturing is done using capturing groups. that means if a string matches the pattern, then parts of that string can be captured using capturing groups...

Finally completed this task. Thanks for help guys!

Quote from sutupud

Март 14, 2013 - 01:29:32

i see two problems whith your regex:
- you have two groups. one should be enough...
- how do you start a non-capturing group? hint: it's not ?=

capturing is done using capturing groups. that means if a string matches the pattern, then parts of that string can be captured using capturing groups...

Why isn't it "?="?
My regex works fine on online demos, but I can't just get it to work on this challenge
"?:" Doesn't seem to have any effect on those demos