ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Using regular expressions
Characters, metacharacters, and metasequences
Flash Player 9 and later, Adobe AIR 1.0 and later
The simplest regular expression is one that matches a sequence of characters, as in the following example:
var pattern:RegExp = /hello/;
However, the following characters, known as metacharacters, have special meanings in regular expressions:
^ $ \ . * + ? ( ) [ ] { } |
For example, the following regular expression matches the letter A followed by zero or more instances of the letter B
(the asterisk metacharacter indicates this repetition), followed by the letter C:
/AB*C/
To include a metacharacter without its special meaning in a regular expression pattern, you must use the backslash (\)
escape character. For example, the following regular expression matches the letter A followed by the letter B, followed
by an asterisk, followed by the letter C:
var pattern:RegExp = /AB\*C/;
A metasequence, like a metacharacter, has special meaning in a regular expression. A metasequence is made up of more
than one character. The following sections provide details on using metacharacters and metasequences.
About metacharacters
The following table summarizes the metacharacters that you can use in regular expressions:
Metacharacter Description
^ (caret) Matches at the start of the string. With the m (multiline) flag set, the caret matches the start of a line as
well (see “Flags and properties” on page 87). Note that when used at the start of a character class, the caret
indicates negation, not the start of a string. For more information, see “Character classes” on page 81.
$(dollar sign) Matches at the end of the string. With the m (multiline) flag set, $ matches the position before a newline
(\n) character as well. For more information, see “Flags and properties” on page 87.
\ (backslash) Escapes the special metacharacter meaning of special characters.
. (dot) Matches any single character.
Also, use the backslash character if you want to use a forward slash character in a regular expression literal,
as in /1\/2/ (to match the character 1, followed by the forward slash character, followed by the character
2).
A dot matches a newline character (\n) only if the s (dotall) flag is set. For more information, see “Flags
and properties” on page 87.
* (star) Matches the previous item repeated zero or more times.
For more information, see “Quantifiers” on page 82.
+ (plus) Matches the previous item repeated one or more times.
For more information, see “Quantifiers” on page 82.
? (question mark) Matches the previous item repeated zero times or one time.
For more information, see “Quantifiers” on page 82.
Last updated 6/6/2012
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