nicolewallace09/match-an-email.md

## match-an-email.md

      
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    Match an Email - Regex Tutorial

This tutorial is going to explain the use of regex to match emails using the expression /^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/. This can be useful when validating emails using applications/technologies such as Node (Inqurier) or MongoDB.
Summary

A regular expression is a sequence of characters that defines a search pattern. This is commonly used to find patterns within a string, find/replace characters within a string or validate input. This tutortial will go walk through the components of a regex and how it applies to matching an email.
Table of Contents


Anchors
Quantifiers
Character Classes
Grouping and Capturing
Bracket Expressions
Greedy and Lazy Match

Regex Components

Anchors

The anchors used in this regex expression for matching an email are ^ , which indicates the beginning of the string and $to indicate the ending of the string. (m), or multiline is not enabled, so the regex will end at $.
Quantifiers

Quantifiers in this regex includes the + operator, which will connect the users email name + email service + .com. Another quantifier for this regex includes {2,6}, which will allow a match range of 2-6 characters for the character set of [a-z\.].
Character Classes

The character class in this expression is \d, which matches a single characters that is a digit from 0-9. It will only match a single digit such as "4", but not "44".
Grouping and Capturing

Capturing group #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 .com.
Bracket Expressions

Bracked expressios for email validation includes the character sets of [a-z0-9_\.-], which is matching any letter a-z and is case senstive. It also matches a character 0-9 and matches the characters "_" , "-" , and "."; [\da-z\.-], which is matching a single digit from 0-9, any character a-z (case senstive), and the characters "." and "-".; [a-z\.] matches any character a-z(case senstive) and the character ".".
Greedy and Lazy Match

This regrex includes greedy matches. Since it includes the + Quantifier, it will match as many times as possible giving back as needed. Another greedy Quantifier used in this regex is {} when matching `{2,6} for the last capture group.
Author

You can view my projects at https://github.com/nicolewallace09.