LET'S CODE: IMPORTANT REGULAR EXPRESSIONS

SOURCE: http://code.tutsplus.com/tutorials/8-regular-expressions-you-should-know--net-6149

1. Matching a Username
Pattern: /^[a-z0-9_-]{3,16}$/

A. String that matches: my-us3r_n4m3
B. String that doesn't match: th1s1s-wayt00_l0ngt0beausername (too long)

2. Matching a Password
Pattern: /^[a-z0-9_-]{6,18}$/

A. String that matches: myp4ssw0rd
B. String that doesn't match: mypa$$w0rd (contains a dollar sign)

3. Matching a Hex Value
Pattern: /^#?([a-f0-9]{6}|[a-f0-9]{3})$/

A. String that matches: #a3c113B.
B. String that doesn't match:#4d82h4 (contains the letter h)

4. Matching a Slug
Pattern: /^[a-z0-9-]+$/

A. String that matches: my-title-here
B. String that doesn't match:​ my_title_here (contains underscores)

5. Matching an Email
Pattern: /^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/

A. String that matches:john@doe.com
B. String that doesn't match:
john@doe.something (TLD is too long)

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

A. String that matches:http://net.tutsplus.com/about
B. String that doesn't match:http://google.com/some/file!.html (contains an exclamation point)

7. Matching an IP Address
Pattern: /^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/


8. Matching an HTML Tag
Pattern:/^<([a-z]+)([^<]+)*(?:>(.*)<\/\1>|\s+\/>)$/

A. String that matches:<a href="http://net.tutsplus.com/">Nettuts+</a>
B. String that doesn't match:<img src="img.jpg" alt="My image>" /> (attributes can't contain greater than signs)