Validating with regular expressions

Posted by / 29-Sep-2017 08:01

Validating with regular expressions

“29/a/2008”, “a/02/2008” – month is invalid, day is invalid 6.

“30/2/2008”, “31/02/2008” – leap year in February has 29 days only 5.

It seems that the checking validation of email addresses is actually two separate problems: 1- Validation of email format: Making sure if the email complies with the format and pattern of emails in RFC 5322 and if the TLD actually exists. For example, although the address The only way to validate an email address is to send an email then wait for response.

Apart of this, here is an url where you can test if your address is RFC822 compliant: .

[1-9] # 01-09 or 1-9 | # .[12][0-9] # 10-19 or 20-29 | # .3[01] # 30, 31 ) #end of group #1 / # follow by a "/" ( # start of group #2 0?

[1-9] # 01-09 or 1-9 | # .1[012] # 10,11,12 ) # end of group #2 / # follow by a "/" ( # start of group #3 (19|20)\d\d # 19[0-9][0-9] or 20[0-9][0-9] ) # end of group #3 The above regular expression is used to validate the date format in “dd/mm/yyyy”, you can easy customize to suit your need.

“31/9/2010”, “31/09/2010” – September has 30 days only 10.

metacharacter match anything INCLUDING line breaks. Java Script by default does not support this since the . This is the best solution and should work 99% of the time is. If you want to match an IP within a string, get rid of the leading ^ and trailing $ to use \b (word boundaries) instead. The regular expression is only useful to validate the format of the date as entered by a user.

Also, single weird leading and/or trailing characters aren’t tested for.

Just imagine you’re doing this before testing modifier to all the regexes to speed up the tests. Here’s a plain text list of all the URLs used in the test.

Here's an example of the above in action: Almost all answers to this questions suggest using Regex to validate emails addresses.

I think Regex is only good for a rudimentary validation.

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Consult the regular expression documentation or the regular expression solutions to common problems section of this page for examples. You can create range of characters using the hyphen character such as A-Z (A to Z).

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