JavaScript RegExp Object
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.
Syntax
var txt=new RegExp(pattern,modifiers);
or more simply:
var txt=/pattern/modifiers;
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- pattern specifies the pattern of an expression
- modifiers specify if a search should be global, case-sensitive, etc.
For a tutorial about the RegExp object, read our
JavaScript RegExp Object tutorial.
Modifiers
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 digit from 0 to 9 |
| [a-z] |
Find any character from lowercase a to lowercase z |
| [A-Z] |
Find any character from uppercase A to uppercase Z |
| [a-Z] |
Find any character from lowercase a to uppercase Z |
| [adgk] |
Find any character in the given set |
| [^adgk] |
Find any character outside the given set |
| [red|blue|green] |
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 or 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 |
RegExp Object Properties
| Property |
Description |
| global |
Specifies if the "g" modifier is set |
| ignoreCase |
Specifies if the "i" modifier is set |
| lastIndex |
The index at which to start the next match |
| multiline |
Specifies if the "m" modifier is set |
| source |
The text of the RegExp pattern |
RegExp Object Methods
| Method |
Description |
| compile() |
Compiles a regular expression |
| exec() |
Tests for a match in a string. Returns a result array |
| test() |
Tests for a match in a string. Returns true or
false |
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