learn-regex

<p align="center">
    <br/>
    <a href="https://github.com/ziishaned/learn-regex">	
        <img src="https://i.imgur.com/bYwl7Vf.png" alt="Learn Regex">
    </a>
</p>

## Translations:

* [English](README.md)
* [German](translations/README-de.md)
* [Español](translations/README-es.md)
* [Français](translations/README-fr.md)
* [Português do Brasil](translations/README-pt_BR.md)
* [中文版](translations/README-cn.md)
* [日本語](translations/README-ja.md)
* [한국어](translations/README-ko.md)
* [Turkish](translations/README-tr.md)
* [Greek](translations/README-gr.md)
* [Magyar](translations/README-hu.md)
* [Polish](translations/README-pl.md)
* [Русский](translations/README-ru.md)
* [Tiếng Việt](translations/README-vn.md)
* [Bahasa Indonesia](translations/README-id.md)
* [فارسی](translations/README-fa.md)
* [עברית](translations/README-he.md)


## What is Regular Expression?

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    <a href="https://gum.co/learn-regex">
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> A regular expression is a group of characters or symbols which is used to find a specific pattern in a text.

A regular expression is a pattern that is matched against a subject string from
left to right. Regular expressions are used to replace text within a string, 
validate forms, extract a substring from a string based on a pattern match, 
and so much more. The term "regular expression" is a mouthful, so you will usually
find the term abbreviated to "regex" or "regexp". 

Imagine you are writing an application and you want to set the rules for when a
user chooses their username. We want to allow the username to contain letters,
numbers, underscores and hyphens. We also want to limit the number of characters
in the username so it does not look ugly. We can use the following regular expression to
validate the username:

<br/><br/>
<p align="center">
  <img src="./img/regexp-en.png" alt="Regular expression">
</p>

The regular expression above can accept the strings `john_doe`, `jo-hn_doe` and
`john12_as`. It does not match `Jo` because that string contains an uppercase
letter and also it is too short.

## Table of Contents

- [Basic Matchers](#1-basic-matchers)
- [Meta Characters](#2-meta-characters)
  - [The Full Stop](#21-the-full-stop)
  - [Character Sets](#22-character-sets)
    - [Negated Character Sets](#221-negated-character-sets)
  - [Repetitions](#23-repetitions)
    - [The Star](#231-the-star)
    - [The Plus](#232-the-plus)
    - [The Question Mark](#233-the-question-mark)
  - [Braces](#24-braces)
  - [Capturing Groups](#25-capturing-groups)
      - [Non-Capturing Groups](#251-non-capturing-groups)
  - [Alternation](#26-alternation)
  - [Escaping Special Characters](#27-escaping-special-characters)
  - [Anchors](#28-anchors)
    - [The Caret](#281-the-caret)
    - [The Dollar Sign](#282-the-dollar-sign)
- [Shorthand Character Sets](#3-shorthand-character-sets)
- [Lookarounds](#4-lookarounds)