I need to test for the following date-type strings:
2004
2004-12
2004-12-01
All of the above would be legal, any other combination would be illegal.
I have been using the following data to test the regex:
'xxxx' Should produce a false result.
'2004' Should produce a true result.
'200412' Should produce a false result.
'20041201' Should produce a false result.
'2004-12' Should produce a true result.
'2004-12-01' Should produce a true result.
My first attempt at a regex is /\d{4}(-\d{2})*/. This produces the
following result:
xxxx is false
2004 is true
200412 is true
20041201 is true
2004-12 is true
2004-12-01 is true
I would prefer that '200412' and '20041201' would fail, i.e. be reported
as false. I'm not sure what's going on with this regex as I would expect
the following:
match the first four numeric characters, then match zero or more
occurrences of a dash character followed by two numeric characters
The next regex /\d{4}(-\d{2})+/ produces the following results:
xxxx is false
2004 is false
200412 is false
20041201 is false
2004-12 is true
2004-12-01 is true
This is closer, but I also want '2004' to be true.
The next regex /\d{4}(?=-\d{2})/ produces the same results as the
previous regex:
xxxx is false
2004 is false
200412 is false
20041201 is false
2004-12 is true
2004-12-01 is true
I've done quite a few regexes in the past but have never used the
positive lookahead assertion before because I have never really
understood it.
Out of the three regexes, I would have expected the first to fulfill my
requirements. I do not understand why it is not, although I suspect it
has something to do with the dash character.
What am I doing wrong here? I should be able to accomplish this test
using a single regex, right?
Dirk Bremer - Systems Programmer II - ESS/AMS - NISC St. Peters
USA Central Time Zone
636-922-9158 ext. 8652 fax 636-447-4471
[EMAIL PROTECTED]
www.nisc.cc
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