This section describes all of the elements of ActionScript regular
expression syntax. As you’ll see, regular expressions can have many
complexities and nuances. You can find detailed resources on regular
expressions on the web and in bookstores. Keep in mind that different
programming environments implement regular expressions in different
ways. ActionScript 3.0 implements regular expressions as defined
in the ECMAScript edition 3 language specification (ECMA-262).
Generally, you use regular expressions that match more complicated
patterns than a simple string of characters. For example, the following
regular expression defines the pattern consisting of the letters
A, B, and C in sequence followed by any digit:
/ABC\d/
The
\d
code represents “any digit.” The backslash
(
\
) character is called the escape character, and
combined with the character that follows it (in this case the letter
d), it has special meaning in the regular expression.
The following regular expression defines the pattern of the letters
ABC followed by any number of digits (note the asterisk):
/ABC\d*/
The asterisk character (
*
) is a
metacharacter
.
A metacharacter is a character that has special meaning in regular
expressions. The asterisk is a specific type of metacharacter called
a
quantifier,
which is used to quantify the amount of repetition
of a character or group of characters. For more information, see
Quantifiers
.
In addition to its pattern, a regular expression can contain
flags, which specify how the regular expression is to be matched.
For example, the following regular expression uses the
i
flag,
which specifies that the regular expression ignores case sensitivity
in matching strings:
/ABC\d*/i
For more information, see
Flags and properties
.
You can use regular expressions with the following methods of
the String class:
match()
,
replace()
,
and
search()
. For more information on these methods,
see
Finding patterns in strings and replacing substrings
.
