ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Using regular expressions
var pattern:RegExp = /(\w+)@(\w+).(com|org)/;
var str:String = "bob@example.com";
trace(pattern.exec(str));
// bob@example.com,bob,example,com
//noncapturing:
var pattern:RegExp = /(\w+)@(\w+).(?:com|org)/;
var str:String = "bob@example.com";
trace(pattern.exec(str));
// bob@example.com,bob,example
A special type of noncapturing group is the lookahead group, of which there are two types: the positive lookahead group
and the negative lookahead group.
Use (?= and ) to define a positive lookahead group, which specifies that the subpattern in the group must match at the
position. However, the portion of the string that matches the positive lookahead group can match remaining patterns
in the regular expression. For example, because (?=e) is a positive lookahead group in the following code, the
character e that it matches can be matched by a subsequent part of the regular expression—in this case, the capturing
group, \w*):
var pattern:RegExp = /sh(?=e)(\w*)/i;
var str:String = "Shelly sells seashells by the seashore";
trace(pattern.exec(str));
// Shelly,elly
Use (?! and ) to define a negative lookahead group that specifies that the subpattern in the group must not match at
the position. For example:
var pattern:RegExp = /sh(?!e)(\w*)/i;
var str:String = "She sells seashells by the seashore";
trace(pattern.exec(str));
// shore,ore
Using named groups
A named group is a type of group in a regular expression that is given a named identifier. Use (?P and ) to
define the named group. For example, the following regular expression includes a named group with the identifier
named digits:
var pattern = /[a-z]+(?P\d+)[a-z]+/;
When you use the exec() method, a matching named group is added as a property of the result array:
var myPattern:RegExp = /([a-z]+)(?P\d+)[a-z]+/;
var str:String = "a123bcd";
var result:Array = myPattern.exec(str);
trace(result.digits); // 123
Here is another example, which uses two named groups, with the identifiers name and dom:
var emailPattern:RegExp =
/(?P(\w|[_.\-])+)@(?P((\w|-)+))+\.\w{2,4}+/;
var address:String = "bob@example.com";
var result:Array = emailPattern.exec(address);
trace(result.name); // bob
trace(result.dom); // example
Note: Named groups are not part of the ECMAScript language specification. They are an added feature in ActionScript 3.0.
Last updated 6/6/2012
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