What does (?: do in a regular expression

Question

I have come across a regular expression that I don\'t fully understand - can somebody help me in deciphering it:

^home(?:\\/|\\/index\\.asp)?(?:\\?.+)?$
<         


        

Answer 1

its really easy every parentheses will create a variable in the memory so you can use the parentheses value afterward so to not save it in memory just put :? in the parentheses like this (?:) and then fill the rest as you need. that's it and nothing else