Regular Expressions Examples
Regular Expressions Examples
Regular Expressions for Username
Pattern : /^[a-z0-9_-]{3,16}$/
Description:
The beginning of the string (^), followed by any lowercase letter (a-z), number (0-9), an underscore, or a hyphen. Next, {3,16} makes sure that are at least 3 of those characters, but no more than 16. And last, the end of the string ($).
Matches:
an-wa3r_t5h3
Doesn’t match:
dgdgd1-www_78chfdhgvsfdsaas (too long)
Regular Expressions for Password
Pattern: /^[a-z0-9_-]{6,18}$/
Description:
Matching a password is very similar to matching a username. The only difference is that instead of 3 to 16 letters, numbers, underscores, or hyphens, we want 6 to 18 of them ({6,18}).
Matches:
anw7ddw90rd
Doesn’t match:
mypa$$w0rd (contains a dollar sign)
Regular Expressions for Email
Pattern: /^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/
Description:
We begin by telling the parser to find the beginning of the string (^). Inside the first group, we match one or more lowercase letters, numbers, underscores, dots, or hyphens. I have escaped the dot because a non-escaped dot means any character. Directly after that, there must be an at sign. Next is the domain name which must be: one or more lowercase letters, numbers, underscores, dots, or hyphens. Then another (escaped) dot, with the extension being two to six letters or dots. I have 2 to 6 because of the country specific TLD’s (.ny.us or .co.uk). Finally, we want the end of the string ($).
Matches:
borntowinanwar@gmail.com
Doesn’t match:
borntowinanwar@gmail.something (TLD is too long)
Regular Expressions for url
Pattern: /^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?$/
Description:
This regex is almost like taking the ending part of the above regex, slapping it between “http://” and some file structure at the end. It sounds a lot simpler than it really is. To start off, we search for the beginning of the line with the caret.
The first capturing group is all option. It allows the URL to begin with “http://”, “https://”, or neither of them. I have a question mark after the s to allow URL’s that have http or https. In order to make this entire group optional, I just added a question mark to the end of it.
Next is the domain name: one or more numbers, letters, dots, or hypens followed by another dot then two to six letters or dots. The following section is the optional files and directories. Inside the group, we want to match any number of forward slashes, letters, numbers, underscores, spaces, dots, or hyphens. Then we say that this group can be matched as many times as we want. Pretty much this allows multiple directories to be matched along with a file at the end. I have used the star instead of the question mark because the star says zero or more, not zero or one. If a question mark was to be used there, only one file/directory would be able to be matched.
Then a trailing slash is matched, but it can be optional. Finally we end with the end of the line.
Matches:
http://zendanwar.wordpress.com/about
Doesn’t match:
http://google.com/some/file!.html (contains an exclamation point)