Syntax for Regular Expression

RegExp Object

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.

Modifiers are used to perform case-insensitive and global searches:

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 

Brackets

Brackets are used to find a range of characters:

Expression Description

[abc]

 

Find any character between the brackets

[^abc]

 

Find any character NOT between the brackets

[0-9]

 

Find any character between the brackets (any digit)

[^0-9]

 

Find any character NOT between the brackets (any non-digit)

(x|y)

 

Find any of the alternatives specified

Metacharacters

Metacharacters are characters with a special meaning: 

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

Quantifiers

Quantifier

Description

n+

Matches any string that contains at least one n

n*

Matches any string that contains zero or more occurrences of n

n?

Matches any string that contains zero or one occurrences of n

n{X}

Matches any string that contains a sequence of X n's

n{X,Y}

Matches any string that contains a sequence of X to Y n's

n{X,}

Matches any string that contains a sequence of at least X n's

n$

Matches any string with n at the end of it

^n

Matches any string with n at the beginning of it

?=n

Matches any string that is followed by a specific string n

?!n

Matches any string that is not followed by a specific string n