JavaScript RegExp Reference
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
/pattern/modifiers;
Example explained:
- /w3schools/i is a regular expression.
- w3schools is a pattern (to be used in a search).
- i is a modifier (modifies the search to be case-insensitive).
For a tutorial about Regular Expressions, read our JavaScript RegExp Tutorial.
Modifiers
Modifiers are used to perform case-insensitive and global searches:
| Modifier | Description |
|---|---|
| g | Perform a global match (find all matches rather than stopping after the first match) |
| i | Perform case-insensitive matching |
| 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, beginning like this: \bHI, end like this: HI\b |
| \B | Find a match, but 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 |
| \udddd | Find the Unicode character specified by a hexadecimal number dddd |
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 |
RegExp Object Properties
| Property | Description |
|---|---|
| constructor | Returns the function that created the RegExp object's prototype |
| global | Checks whether the "g" modifier is set |
| ignoreCase | Checks whether the "i" modifier is set |
| lastIndex | Specifies the index at which to start the next match |
| multiline | Checks whether the "m" modifier is set |
| source | Returns the text of the RegExp pattern |
RegExp Object Methods
| Method | Description |
|---|---|
| compile() | Deprecated in version 1.5. 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 |
| toString() | Returns the string value of the regular expression |
