Posted by: lrrp | January 15, 2013

Some useful regular expressions for efficient web development

In programming, regular expressions are a very useful tool designed to validate, search, and match text patterns. In this article, I have compiled more than 10 incredibly useful regular expressions, for any language, that will probably be very beneficial to you.

Validate an URL

Is a particular url valid? The following regexp will let you know.

/^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \?=.-]*)*\/?$/


Validate US phone number

This regexp will verify that a US phone number is valid.



Test if a password is strong

Weak passwords are one of the quickest ways to get hacked. The following regexp will make sure that:

  • Passwords will contain at least (1) upper case letter
  • Passwords will contain at least (1) lower case letter
  • Passwords will contain at least (1) number or special character
  • Passwords will contain at least (8) characters in length
  • Password maximum length should not be arbitrarily limited


Validate US zip code

When building a registration form, it is common to ask the user’s zip code. As forms are often boring, there’s a strong chance that the user will try to register false data. This regular expression will make sure he entered a valid American zip code.



Validate Canadian postal code

This regexp is very similar to the previous one, but it will match Canadian postal codes instead.

^[ABCEGHJ-NPRSTVXY]{1}[0-9]{1}[ABCEGHJ-NPRSTV-Z]{1}[ ]?[0-9]{1}[ABCEGHJ-NPRSTV-Z]{1}[0-9]{1}$


Grab unclosed img tags

As you probably know, the xhtml standard requires all tags to be properly closed. This regular expression will search for unclosed img tags. It could be easily modified to grab any other unclosed html tags.



Find all CSS attributes

This regexp will find CSS attributes, such as background:red; or padding-left:25px;.



Validate an IBAN

I have recently worked on a banking application and this one was definitely a life-saver. It will verify that the given IBAN is valid.



Validate a BIC code

Another one very useful for any banking application or website: This regexp will validate a BIC code.




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