In this tutorial it will explain how a specific expression, or regex, functions by breaking down each part of the expression and describing what it does, SO THAT you can understand the search pattern that the regex defines.
The featured regex in this tutorial is designed to match specific patterns within text. Regex is an encoded text string that computer programmers use as search patterns for matching sets of strings. These expressions provide a concise and flexible way of matching various text strings. As we dive into its components, you'll begin to understand how it all functions.
- Anchors
- Quantifiers
- Grouping Constructs
- Bracket Expressions
- Character Classes
- The OR Operator
- Flags
- Character Escapes
These characters give details about the location within a particular string a user is trying to search. It helps in searching within lines. Usually, for finding character A in a string, you can use the following characters to find a match within a line:
A$: Helps in matching at the end of a line. ^A: Helps in matching at the beginning of a line.
Quantifiers help in defining quantities for a search string. Some commonly used quantifiers are:
n+: Matches any string containing at least one n. n?: Matches any string containing zero or one occurrence of n. n*: Matches any string containing zero or more occurrences of n.
Allow you to group parts of a pattern together. They are enclosed within parentheses ()
(abc): This creates a capturing group that matches the sequence "abc". (?:grouping)
Square Brackets- shows one character of the regex. [a-zA-Z] Parenetheses- Creates a sequence or sub-expression. (a-za-Z)
Help you define parameters for the type of text you want to search. For instance, you can use [0-9] to search for numerical ranges. Interestingly, regex allows programmers to find letter ranges or support alternate spellings. For example, so[ml]e matches both some and sole. Some commonly used character sets are:
[a-z]: Helps in matching lowercase letters from a to z. [A-Z]: Helps in matching uppercase letters from A to Z. [0-9]: Helps match a range of numbers from 0 to 9. [.]: Helps match any character, except line break characters.
Is signified by the | character. The OR Operator is used when the user wants to inform the regex that not every search parameter must be met. Rather, it can be one or several search parameters being met to yield a result.
pattern1|pattern2
Also called modifiers or options, are special tokens that alter the behavior of the regex pattern matching. These can be applied at the beginning or end of the regex pattern and affect how the pattern is interpreted and matched against the input text.
/pattern/gi
Are special sequences that represent characters with special meaning or characters that are difficult to represent directly in a regex pattern. These escapes begin with a backslash \ followed by a character, and they are used to match specific characters or character classes.
\d: Matches any digit character (equivalent to [0-9]).
This tutorial is made by Kayleena Bellew, I am currently a student in full stack web-dev at KU, a regex beginner but did a lot of research to get the most informational tutorial. Check out my profile at (https://github.com/KKBellew/ ).