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Simple and Useful JavaScript Regular Expression Tutorial

, 16 Jul 2012 CPOL
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This post discusses some simple and useful JavaScript Regular Expressions

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

Character Escapes  (Metacharacters)

Metacharacter  Description
Find a single character, except newline or line terminator 
\w Find a word character 
\W  Find a non-word character 
\d Find a digit 
\D Find a non-digit character 
\s Find a whitespace character 
\S Find a non-whitespace character 
\b Find a match at the beginning/end of a word 
\B Find a match not at the beginning/end of a word 
\0  Find a NUL character
\n Find a new line character 
\f  Find a form feed character 
\r  Find a carriage return character 
\t  Find a tab character 
\v  Find a vertical tab character 
\xxx Find the character specified by an octal number xxx 
\xdd Find the character specified by a hexadecimal number dd 
\uxxxx Find the Unicode character specified by a hexadecimal number xxxx 

Metacharacter table from W3Schools.  

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

  • 19 May, 2011: Initial version.
  • 1 June, 2011: Added sample source code.
  • 16 July, 2012: Add metacharacters table.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Afshin Mehrabani
CEO usabli.ca
Iran (Islamic Republic Of) Iran (Islamic Republic Of)
I am a web developer, the co-founder of usabli.ca.
I love programming and also new technologies on Web Developing such as HTML5 and I always split my time between programming and reading.
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Comments and Discussions

 
GeneralMy vote of 5 PinmemberAbdul Quader Mamun14-Aug-12 3:28 
QuestionNot an article PinmemberGanesanSenthilvel16-Jul-12 3:48 
QuestionRe: Not an article PinmemberAfshin Mehrabani16-Jul-12 6:11 
GeneralMy vote of 1 PinmvpDave Kreskowiak16-Jul-12 2:46 
GeneralMy vote of 1 Pinmemberdavidlow7023-May-11 15:14 
GeneralThanks PinmemberAhmad Hyari21-May-11 9:39 
Looking forward for the next article
Leader

GeneralMy vote of 3 PinmvpAspDotNetDev20-May-11 11:37 
GeneralRe: My vote of 3 PinmemberAfshin Mehrabani21-May-11 7:28 
GeneralRe: My vote of 3 Pinmemberdavidlow7023-May-11 15:21 

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