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Regular exp In JavaScript
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
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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円
The NUL character (\u0000)
\t
Tab (\u0005)
\n
Newline (\u000A)
\f
Form feed (\u000C)
\r
Carriage return (\u000D)
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