What exactly is this regular expression doing?

Question

I'm looking over some code and found the following regex:

var querystring = querystring.replace(/[^&]+=\.?(?:&|$)/g, '')

Is this taking the querystring and replacing all values that begin with an ampersand or question mark with a space? Is there more going on here that I don't see?

You're logical explanation is much appreciated and help gain a little more understanding of regex. Thanks!

Answer 1

It appears to remove those parameters from the query string whose value is:

1. empty
2. equal to .

For example:

"remove1=&remove2=.&keep1=..&keep2=a&keep3=b".replace(/[^&]+=\.?(?:&|$)/g, '')
// returns "keep1=..&keep2=a&keep3=b"

Answer 2

[^&]+ one or more non "&" characters

= a literal "=" character

\\.? an optional "."

(?:&|$) a "&" character or the end of the string

Would eg match

Foobar=.&
A=