RegEx Tutorial

gistfile1.txt

In this Gist I will give a tutorial of RegEx

Regex Tutorial

In this tutorial I am going to explain the use of regex to match emails using the expression. Regex stands for regular expression. they are used as a sequence keyboard characters, that specify a type of search pattern. In this tutorial, I will be using this regex /^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/. This expression can be used to validate emails using applications, websites and other technology like MongoDB.

Summary

A regex (regular expression) is a sequence of characters that represents a specific search pattern. They are usually used to find a particular pattern, replace characters or even validate specific characters within a string. When used in JavaScript they are used as objects. In this tutorial I will walk you through the components of a regex and how it's used in validating an email.

Table of Contents

• Anchors
• Quantifiers
• Grouping and Capturing
• Bracket Expressions

Regex Components

Anchors

Anchors, which are the opener and closer of the regex, are used in the email expression to match are ^ , the beginning and $ which indicates the ending of the string.

Quantifiers

Quantifiers in this regex include + , used as an operator, that will connect the username to the email extension then to then domain (username@email.com). Another quantifier for this regex includes {2,6}, which will make sure the domain matches a range of 2-6 characters for the character set of [a-z\.].

Grouping and Capturing

Group and Capturing is when a group of the #1 in this expression is ([a-z0-9_\.-]+) that matches the user email name. The second capturing group is ([\da-z\.-]+) which will match the email service. Then lastly, capture group #3 is ([a-z\.]{2,6}) to capture the domain.

Bracketed Expressions

Bracketed Expressions are the character sets within the expression that hold the above captured groups. in the character set used above, [a-z0-9_\.-], states that the username, of the email can include a combination of letters, numbers and the special characters ". -_". They are held in the actual [].

Author

check out my github at https://github.com/ra8200 .