JavaScript Tutorial

Regular exp In JavaScript
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javascript also provide Regular expressions that is very powerful tools for performing pattern matches.that is also used in PERL programmers and UNIX shell programmers .

An regular expression is written in the form of pattern or modifiers where pattern is the regular expression itself and modifiers are a series of characters indicating various options. The "modifiers" part is optional.

There are characters which have special use in regular exps : [ \ ^ $ . | ? * + ( ).

There are Manely two methods for creating a RegExp object.

  • RegExp Literal
  • RegExp Object Constructor
Syntax :
var pattern = new RegExp(pattern, modifiers);
                             OR
var pattern = /pattern/modifiers;

Brackets are used to find a range of characters :

Expression Description
[a-z] It matches any character from lowercase a through lowercase z.
[abc] Find any character between the brackets
[A-Z] It matches any character from uppercase A through uppercase Z.
[^abc] Find any character NOT between the brackets
(x|y) Find any of the alternatives specified
[0-9] It matches any decimal digit from 0 through 9.

Modifiers used in reg() :

Modifier Meaning Description
i Ignore Case its Perform a case-insensitive matching
g Global Search its Perform a global match that's find all matches rather than stopping after the first match.
m Multiline Input its Perform a multiline matching

 

Regular Expression Quantifiers :

Expression Description
* 0 or more
+ 1 or more
? 0 or 1
{2} Exactly 2
{2, 5} Between 2 and 5
{2,} 2 or more

Literal characters :

Character Description
\0 The NUL character (\u0000)
\t Tab (\u0005)
\n Newline (\u000A)
\f Form feed (\u000C)
\r Carriage return (\u000D)
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