Developer always want user registration to be easy and comprehensive, we can make it very interesting by letting the user know the pattern their username will take after completing the registration. They can see if the username look cool enough or they can change it to see what is going to come out of it. The main reason for creating this tutorial is for us to learn how to create a very interactive application with the combination of JavaScript and HTML5.We are going to create a username picker that will change their username right in front of their eyes. 

It is the Duty of every developer to validate and make sure that all the data that users supply are valid before it gets to the database, Today I will ensure we touch both sever side and client side validation using the regular expression. "In theoretical computer science and formal language theory, a regular expression (abbreviated regex or regexp and sometimes called a rational expression) is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. "find and replace"-like operations. The concept arose in the 1950s, when the American mathematician Stephen Kleene formalized the description of a regular language, and came into common use with the Unix text processing utilities ed, an editor, and grep (global regular expression print), a filter." - Wikipedia.