Regular Expression in Javascript

Pattern	Description
Escaping
\	Escapes special characters to literal and literal characters to special. E.g: /\(s\)/ matches '(s)' while /(\s)/ matches any whitespace and captures the match.
Quantifiers
{n}, {n,}, {n,m}, *, +, ?	Quantifiers match the preceding subpattern a certain number of characters. The subpattern can be a single character, an escape sequence, a pattern enclosed by parentheses or a character set. {n} matches exactly n times. {n,} matches n or more times. {n,m} matches n to m times. * is short for {0,}. Matches zero or more times. + is short for {1,}. Matches one or more times. ? is short for {0,1}. Matches zero or one time. E.g: /o{1,3}/ matches 'oo' in "tooth" and 'o' in "nose".
Pattern delimiters
(pattern), (?:pattern)	Matches entire contained pattern. (pattern) captures match. (?:pattern) doesn't capture match E.g: /(d).\1/ matches and captures 'dad' in "abcdadef" while /(?:.d){2}/ matches but doesn't capture 'cdad'. Note: (?:pattern) is very badly supported in older browsers.
Lookaheads
(?=pattern), (?!pattern)	A lookahead matches only if the preceeding subexpression is followed by the pattern, but the pattern is not part of the match. The subexpression is the part of the regular expression which will be matched. (?=pattern) matches only if there is a following pattern in input. (?!pattern) matches only if there is not a following pattern in input. E.g: /Win(?=98)/ matches 'Win' only if 'Win' is followed by '98'. Note: Support for lookaheads is lacking in most but the newest browsers.
Alternation
|	Alternation matches content on either side of the alternation character. E.g: /(a|b)a/ matches 'aa' in "dseaas" and 'ba' in "acbab".
Character sets
[characters], [^characters]	Matches any of the contained characters. A range of characters may be defined by using a hyphen. [characters] matches any of the contained characters. [^characters] negates the character set and matches all but the contained characters E.g: /[abcd]/ matches any of the characters 'a', 'b', 'c', 'd' and may be abbreviated to /[a-d]/. Ranges must be in ascending order, otherwise they will throw an error. (E.g: /[d-a]/ will throw an error.) /[^0-9]/ matches all characters but digits. Note: Most special characters are automatically escaped to their literal meaning in character sets.
Special characters
^, $, ., ? and all the highlighted characters above in the table.	Special characters mean characters that match something else than what they appear as. ^ matches beginning of input (or new line with m flag). $ matches end of input (or end of line with m flag). . matches any character except a newline. ? directly following a quantifier makes the quantifier non-greedy (makes it match minimum instead of maximum of the interval defined). E.g: /(.)*?/ matches nothing or '' in all strings. Note: Non-greedy matches are not supported in older browsers such as Netscape Navigator 4 or Microsoft Internet Explorer 5.0.
Literal characters
All characters except those with special meaning.	Mapped directly to the corresponding character. E.g: /a/ matches 'a' in "Any ancestor".
Backreferences
\n	Backreferences are references to the same thing as a previously captured match. n is a positive nonzero integer telling the browser which captured match to reference to. /(\S)\1(\1)+/g matches all occurrences of three equal non-whitespace characters following each other. /<(\S+).*>(.*)<\/\1>/ matches any tag. E.g: /<(\S+).*>(.*)<\/\1>/ matches ' text ' in "text text text".
Character Escapes
\f, \r, \n, \t, \v, \0, [\b], \s, \S, \w, \W, \d, \D, \b, \B, \cX, \xhh, \uhhhh	\f matches form-feed. \r matches carrriage return. \n matches linefeed. \t matches horizontal tab. \v matches vertical tab. \0 matches NUL character. [\b] matches backspace. \s matches whitespace (short for [\f\n\r\t\v\u00A0\u2028\u2029]). \S matches anything but a whitespace (short for [^\f\n\r\t\v\u00A0\u2028\u2029]). \w matches any alphanumerical character (word characters) including underscore (short for [a-zA-Z0-9_]). \W matches any non-word characters (short for [^a-zA-Z0-9_]). \d matches any digit (short for [0-9]). \D matches any non-digit (short for [^0-9]). \b matches a word boundary (the position between a word and a space). \B matches a non-word boundary (short for [^\b]). \cX matches a control character. E.g: \cm matches control-M. \xhh matches the character with two characters of hexadecimal code hh. \uhhhh matches the Unicode character with four characters of hexadecimal code hhhh.

Usage

Now, knowing how a RegExp is written is only half the game. To gain anything from them you have to know how to use them too. There are a number of ways to implement a RegExp, some through methods belonging to the String object, some through methods belonging to the RegExp object. Whether the regular expression is declared through an object constructor or a literal makes no difference as to the usage.

Description	Example
RegExp.exec(string)
Applies the RegExp to the given string, and returns the match information.	var match = /s(amp)le/i.exec("Sample text") match then contains ["Sample","amp"]
RegExp.test(string)
Tests if the given string matches the Regexp, and returns true if matching, false if not.	var match = /sample/.test("Sample text") match then contains false
String.match(pattern)
Matches given string with the RegExp. With g flag returns an array containing the matches, without g flag returns just the first match or if no match is found returns null.	var str = "Watch out for the rock!".match(/r?or?/g) str then contains ["o","or","ro"]
String.search(pattern)
Matches RegExp with string and returns the index of the beginning of the match if found, -1 if not.	var ndx = "Watch out for the rock!".search(/for/) ndx then contains 10
String.replace(pattern,string)
Replaces matches with the given string, and returns the edited string.	var str = "Liorean said: My name is Liorean!".replace(/Liorean/g,'Big Fat Dork') str then contains "Big Fat Dork said: My name is Big Fat Dork!"
String.split(pattern)
Cuts a string into an array, making cuts at matches.	var str = "I am confused".split(/\s/g) str then contains ["I","am","confused"]

Liorean is a twenty one years old medical student and hobbyist web designer mostly working with JavaScript and CSS, DOM and the newest html standards available. His personal dwelling on the net can be found at liorean@web-graphics.com.

JavaScript String Replace All

The JavaScript function for String Replace replaces the first occurrence in the string. The function is similar to the php function str_replace and takes two simple parameters. The first parameter is the pattern to find and the second parameter is the string to replace the pattern with when found. The javascript function does not Replace All...

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JavaScript:

1. str = str.replace(”find”,”replace”)

To ReplaceAll you have to do it a little differently. To replace all occurrences in the string, use the g modifier like this:

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JavaScript: str = str.replace(/find/g,”replace”)