How to use regex ?

How to use
regex ?

Why use regex ?

Regex is really powerful in searching and manipulating text strings. One line of regex can easily replace several dozen lines of programming codes. Regex is supported in almost all the scripting languages (such as Perl, Python, PHP, and JavaScript); as well as general purpose programming languages such as Java;

You can filter all string you want, each letter in a sentence, in a paragraph, you can check if there is/are number at the eatly, the middle or the end of a sentence etc...

Ready to learn how use them ?

To start

A regex start with / and finish with /.

Example : /^\d+$/

"ahhhh ! what means this ???"
Wait ! Now, you know a regex start and end with /. Here, \d means digits. So we have a regex who inspect if there is digits. Digits means number (0,1,2,3,4,5,6,7,8,9). the \d can be replaced by
[0-9]. The [ ] means all that is between and here it's from 0 to 9. So we need to write a - for the "to". The ^ and the $ are used to say that the number need to be at the early or at the end of the string. To finish, the + means the string can have one or more digits.

Expressions

Table of all the expressions you can find in a regex :

Expression	Meaning

Some examples

Positive integers literal : /[1-9][0-9]*|0/

An identifier : /[a-zA-Z_][0-9a-zA-Z_]*/

An image file name : /^\w+\.(gif|png|jpg|jpeg)$/i

Email adress : /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/

HTTP adress: /^http:\/\/\S+(\/\S+)*(\/)?$/

Pattern

For advanced users, who like create patterns :

(?:pattern) = non-capturing group
(?=pattern) = positive look ahead
(?!pattern) = negative look ahead
(?<=pattern) = positive look behind
(?<!pattern) = negative look behind

My codes

In this code you will find 2 type of regex :
Best Converter decimal / binary

My other codes related to help you :
Make draggable elements
unselectable elements
Create a scroll top
Create search input
Create JS classes

How to use Regex ?