The purppose of this tutorial is to give users information on what Regex is and how to use it. The tutorial will provide a summary as well as detail examples for a specific regex provide.
Regular Expression, otherwise known as "Regex"; is a sequence of characters that defines a specific search pattern. Regex can be used to find certain patterns of characters within a string. However, Regex is most frequently used to validate inputs from a user. An example is the following Regex provided below.
/^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/
The regex is used to verify that the user input is a valid email address. More details of this Regular Expression will be provided below
Anchors allow the strings to match your input. Those anchors would be ^ and $. The ^ anchor matches the beginning of the string; while the $ anchor matches the end of the string. So for the example of the email validation, "/^([a-z0-9_.-]+)@([\da-z.-]+).([a-z.]{2,6})$/", the anchor will match the exact string of the email. The reason is because both characters are at the beginning and end of the validation.
Quantifiers are the characters: *, +, ?, and {}. Quantifiers match the specified quantity of the previous token. So an example with the email validation, "/^([a-z0-9_.-]+)@([\da-z.-]+).([a-z.]{2,6})$/", the quantifier will match the tokens from 2 to 6 within {} and match the string with +.
OR Operator are the characters: | and []. OR Operator matches the characters within the tokens. So an example with the email validation is, "/^([a-z0-9_.-]+)@([\da-z.-]+).([a-z.]{2,6})$/", The [] looks for those tokens and matches them specifically.
Grouping and Capturing are the characters: (). It groups multiple tokens together to create a capture group for extracting a substring. So with the email validation, "/^([a-z0-9_.-]+)@([\da-z.-]+).([a-z.]{2,6})$/", it is capturing the group together within the parentheses.
Bracket Expression uses the characters: []. Bracket Expressions matches the string between the characters. With the email validation, "/^([a-z0-9_\.-]+)@([\da-z\.-]+).([a-z\.]{2,6})$/", the Bracket Expression matches the characters within [] expresssion.
Greedy operators are the characters: * + {}. The lazy operator is the character: ?. Greedy operators match the token to the preceding token. The lazy operator makes the quantifier lazy which makes it match as few characters as possible. So in the email validation, "/^([a-z0-9_.-]+)@([\da-z.-]+).([a-z.]{2,6})$/", there is no lazy operator. However, it does contain greedy operators which allows the tokens to match specifically.
The gist was created by Juan Garcia. Juan is currently attending a Coding Boot Camp at Michigan State University. He received his Bachelor's Degree in Computer Engineering with a Minor in Computer Science. You can check the links below to know more about Juan: