JavaScript/Regular Expressions
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[edit] Regular Expressions
JavaScript implements regular expressions (regex for short) when searching for matches within a string. As with other scripting languages, this allows searching beyond a simple letter-by-letter match, and can even be used to parse strings in a certain format.
Unlike strings, regular expressions are bound by the slash (/) character, and may have some options appended.
Regular expressions most commonly appear in conjunction with the string.match() and string.replace() methods.
[edit] Compatibility
JavaScript's set of regular expressions follows the extended set. While copying a Regex pattern from JavaScript to another location may work as expected, some older programs may not function as expected.
- In the search term, \1 is used to back reference a matched group, as in other implementations.
- In the replacement string, $1 is substituted with a matched group in the search, instead of \1.
- Example: "abbc".replace(/(.)\1/g, "$1") => "abc"
- | is magic, \| is literal
- ( is magic, \( is literal
[edit] Examples
- Matching
- string = "Hello world!".match(/world/);
- stringArray = "Hello world!".match(/l/g); // Matched strings are returned in a string array
- Replacement
- string = string.replace(/expression without quotation marks/g, "replacement");
- string = string.replace(/escape the slash in this\/way/g, "replacement");
- string = string.replace( ... ).replace ( ... ). replace( ... );
- Test
- if (string.match(/regexp without quotation marks/)) {
[edit] Modifiers
| Modifier | Note |
|---|---|
| g | Global. The list of matches is returned in an array. |
| i | Case-insensitive search |
| m |
Multiline. If the operand string has multiple lines, ^ and $ match the beginning and end of each line within the string, instead of matching the beginning and end of the whole string only.
|
[edit] Operators
| Operator | Effect |
|---|---|
| \b | Matches boundary of a word. |
| \w | Matches an alphanumeric character, including "_". |
| \W | Negation of \w. |
| \s | Matches a whitespace character (space, tab, newline, formfeed) |
| \S | Negation of \s. |
| \d | Matches a digit. |
| \D | Negation of \d. |
[edit] See also
- Regular Expressions - a Wikibook dedicated to regular expressions.
- Perl Regular Expressions Reference - a chapter devoted to regular expressions in a book about the Perl programming language.
[edit] External links
- JavaScript RegExp Object Reference at W3schools.com
- JavaScript RexExp Tester
