Simple and Useful JavaScript Regular Expression Tutorial
Introduction
Regular Expression is a very important part of any language programming because of its ability to help programmers to write fast and pure applications.
You Don't Know What a Regular Expression Is?
A regular expression is an object that describes a pattern of characters.
Regular expressions are used to perform pattern-matching and "search-and-replace" functions on text.
Web developer can also use Regular Expression in JavaScript. Now I describe some simple examples of using Regular Expression in JavaScript.
The overall syntax should look like:
/pattern/modifiers
- pattern specifies the search pattern
- modifiers specify if our search should be case-sensitive, global, etc.
Modifiers Table
| Modifier | Description |
| i | Perform case-insensitive matching |
| g | Perform a global match (find all matches rather than stopping after the first match) |
| m | Perform multiline matching |
To compile and use Regular Expression, you can use three useful functions.
Regular Expression Object Methods
| Method | Description |
compile() |
Compiles a regular expression |
exec() |
Tests for a match in a string. Returns the first match |
test() |
Tests for a match in a string. Returns true or false |
Example
Test sentence: Sometext sometext sometext
| Expression | Test Result |
| /sometext/ | Sometext sometext sometext |
| /sometext/i | Sometext sometext sometext |
| /sometext/g | Sometext sometext sometext |
| /sometext/gi | Sometext sometext sometext |
| /some/ | Sometext sometext sometext |
| /some/i | Sometext sometext sometext |
| /some/g | Sometext sometext sometext |
| /some/ig | Sometext sometext sometext |
It's easy!
In the next article, I will show you Regular Expression performance in some cases and also how to make simple and pure Regular Expressions.
History
- 19th May, 2011: Initial version