RegExp

Package	Top Level
Class	public dynamic class RegExp
Inheritance	RegExp Object

Language Version:

ActionScript 3.0

Runtime Versions:

AIR 1.0 Flash Player 9

The RegExp class lets you work with regular expressions, which are patterns that you can use to perform searches in strings and to replace text in strings.

You can create a new RegExp object by using the new RegExp() constructor or by assigning a RegExp literal to a variable:

 var pattern1:RegExp = new RegExp("test-\\d", "i");
     var pattern2:RegExp = /test-\d/i;

For more information, see "Using Regular Expressions" in Programming ActionScript 3.0.

View the examples

	Property	Defined By
		constructor : Object A reference to the class object or constructor function for a given object instance.	Object
		dotall : Boolean [read-only] Specifies whether the dot character (.) in a regular expression pattern matches new-line characters.	RegExp
		extended : Boolean [read-only] Specifies whether to use extended mode for the regular expression.	RegExp
		global : Boolean [read-only] Specifies whether to use global matching for the regular expression.	RegExp
		ignoreCase : Boolean [read-only] Specifies whether the regular expression ignores case sensitivity.	RegExp
		lastIndex : Number Specifies the index position in the string at which to start the next search.	RegExp
		multiline : Boolean [read-only] Specifies whether the m (multiline) flag is set.	RegExp
		prototype : Object [static] A reference to the prototype object of a class or function object.	Object
		source : String [read-only] Specifies the pattern portion of the regular expression.	RegExp

	Method	Defined By
		RegExp(re:String, flags:String) Lets you construct a regular expression from two strings.	RegExp
		exec(str:String):Object Performs a search for the regular expression on the given string str.	RegExp
		hasOwnProperty(name:String):Boolean Indicates whether an object has a specified property defined.	Object
		isPrototypeOf(theClass:Object):Boolean Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter.	Object
		propertyIsEnumerable(name:String):Boolean Indicates whether the specified property exists and is enumerable.	Object
		setPropertyIsEnumerable(name:String, isEnum:Boolean = true):void Sets the availability of a dynamic property for loop operations.	Object
		test(str:String):Boolean Tests for the match of the regular expression in the given string str.	RegExp
		toLocaleString():String Returns the string representation of this object, formatted according to locale-specific conventions.	Object
		toString():String Returns the string representation of the specified object.	Object
		valueOf():Object Returns the primitive value of the specified object.	Object

dotall

property

dotall:Boolean [read-only]

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 9, AIR 1.0

Specifies whether the dot character (.) in a regular expression pattern matches new-line characters. Use the s flag when constructing a regular expression to set dotall = true.

Implementation
public function get dotall():Boolean

Example ( How to use this example )

The following example shows the effect of the s (dotall) flag on a regular expression:

var str:String = "<p>Hello\n"
        + "again</p>"
        + "<p>Hello</p>";

var pattern:RegExp = /<p>.*?<\/p>/;
trace(pattern.dotall) // false
trace(pattern.exec(str)); // <p>Hello</p>

pattern = /<p>.*?<\/p>/s;
trace(pattern.dotall) // true
trace(pattern.exec(str));

extended

property

extended:Boolean [read-only]

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 9, AIR 1.0

Specifies whether to use extended mode for the regular expression. When a RegExp object is in extended mode, white space characters in the constructor string are ignored. This is done to allow more readable constructors.

Use the x flag when constructing a regular expression to set extended = true.

Implementation
public function get extended():Boolean

Example ( How to use this example )

The following example shows different ways to construct the same regular expression. In each, the regular expression is to match a phone number pattern of xxx-xxx-xxxx or (xxx) xxx-xxxx or (xxx)xxx-xxxx. The second regular expression uses the x flag, causing the white spaces in the string to be ignored.

var rePhonePattern1:RegExp = /\d{3}-\d{3}-\d{4}|\(\d{3}\)\s?\d{3}-\d{4}/; 
var str:String = "The phone number is (415)555-1212.";

trace(rePhonePattern1.extended) // false
trace(rePhonePattern1.exec(str)); // (415)555-1212

var rePhonePattern2:RegExp = / \d{3}-\d{3}-\d{4}  |   \( \d{3} \) \ ? \d{3}-\d{4}  /x; 
trace(rePhonePattern2.extended) // true
trace(rePhonePattern2.exec(str)); // (415)555-1212

global

property

global:Boolean [read-only]

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 9, AIR 1.0

Specifies whether to use global matching for the regular expression. When global == true, the lastIndex property is set after a match is found. The next time a match is requested, the regular expression engine starts from the lastIndex position in the string. Use the g flag when constructing a regular expression to set global to true.

Implementation
public function get global():Boolean

Example ( How to use this example )

The following example shows the effect setting the g (global) flag on the exec() method:

var pattern:RegExp = /foo\d/; 
var str:String = "foo1 foo2";
trace(pattern.global); // false
trace(pattern.exec(str)); // foo1
trace(pattern.lastIndex); // 0
trace(pattern.exec(str)); // foo1

pattern = /foo\d/g;
trace(pattern.global); // true
trace(pattern.exec(str)); // foo1
trace(pattern.lastIndex); // 4
trace(pattern.exec(str)); // foo2

ignoreCase

property

ignoreCase:Boolean [read-only]

Language Version:

ActionScript 3.0

Runtime Versions:

AIR 1.0 Flash Player 9

Specifies whether the regular expression ignores case sensitivity. Use the i flag when constructing a regular expression to set ignoreCase = true.

Implementation
public function get ignoreCase():Boolean

Example ( How to use this example )

The following example shows the effect of setting the i (ignoreCase) flag:

var pattern:RegExp = /bob/; 
var str:String = "Bob bob";
trace(pattern.ignoreCase); // false
trace(pattern.exec(str)); // bob

pattern = /bob/i;
trace(pattern.ignoreCase); // true
trace(pattern.exec(str)); // Bob

lastIndex

property

lastIndex:Number

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 9, AIR 1.0

Specifies the index position in the string at which to start the next search. This property affects the exec() and test() methods of the RegExp class. However, the match(), replace(), and search() methods of the String class ignore the lastIndex property and start all searches from the beginning of the string.

When the exec() or test() method finds a match and the g (global) flag is set to true for the regular expression, the method automatically sets the lastIndex property to the index position of the character after the last character in the matching substring of the last match. If the g (global) flag is set to false, the method does not set the lastIndexproperty.

You can set the lastIndex property to adjust the starting position in the string for regular expression matching.

Implementation
public function get lastIndex():Number
public function set lastIndex(value:Number):void

Example ( How to use this example )

The following example shows the effect of setting the lastIndex property, and it shows how it is updated after a call to the exec() method on a regular expression in which the g (global) flag is set:

var pattern:RegExp = /\w\d/g; 
var str:String = "a1 b2 c3 d4";
pattern.lastIndex = 2; 
trace(pattern.exec(str)); // b2
trace(pattern.lastIndex); // 5
trace(pattern.exec(str)); // c3
trace(pattern.lastIndex); // 8
trace(pattern.exec(str)); // d4
trace(pattern.lastIndex); // 11
trace(pattern.exec(str)); // null

multiline

property

multiline:Boolean [read-only]

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 9, AIR 1.0

Specifies whether the m (multiline) flag is set. If it is set, the caret (^) and dollar sign ($) in a regular expression match before and after new lines. Use the m flag when constructing a regular expression to set multiline = true.

Implementation
public function get multiline():Boolean

Example ( How to use this example )

The following example shows the effect setting the m (multiline) flag:

var pattern:RegExp = /^bob/; 
var str:String = "foo\n"
                + "bob";
trace(pattern.multiline); // false
trace(pattern.exec(str)); // null

pattern = /^bob/m;
trace(pattern.multiline); // true
trace(pattern.exec(str)); // bob

source

property

source:String [read-only]

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 9, AIR 1.0

Specifies the pattern portion of the regular expression.

Implementation
public function get source():String

Example ( How to use this example )

The following code outputs the source parameter for two regular expressions:

var re1:RegExp = /aabb/gi;
trace (re1.source); // aabb

var re2:RegExp = new RegExp("x+y*", "i");
trace(re2.source); // x+y*

Constructor Detail

()

Constructor

public function RegExp(re:String, flags:String)

Language Version:

ActionScript 3.0

Runtime Versions:

AIR 1.0 Flash Player 9

Lets you construct a regular expression from two strings. One string defines the pattern of the regular expression, and the other defines the flags used in the regular expression.

Parameters

re:String — The pattern of the regular expression (also known as the constructor string). This is the main part of the regular expression (the part that goes within the "/" characters).

Notes:

Do not include the starting and trailing "/" characters; use these only when defining a regular expression literal without using the constructor. For example, the following two regular expressions are equivalent:
```
 var re1:RegExp = new RegExp("bob", "i"); 
        var re2:RegExp = /bob/i;
```
In a regular expression that is defined with the RegExp() constructor method, to use a metasequence that begins with the backslash (\) character, such as \d (which matches any digit), type the backslash character twice. For example, the following two regular expressions are equivalent:
```
 var re1:RegExp = new RegExp("\\d+", ""); 
        var re2:RegExp = /\d/;
```
In the first expression, you must type the backlash character twice in this case, because the first parameter of the RegExp() constructor method is a string, and in a string literal you must type a backslash character twice to have it recognized as a single backslash character.

flags:String — The modifiers of the regular expression. These can include the following:

g — When using the replace() method of the String class, specify this modifier to replace all matches, rather than only the first one. This modifier corresponds to the global property of the RegExp instance.
i — The regular expression is evaluated without case sensitivity. This modifier corresponds to the ignoreCase property of the RegExp instance.
s — The dot (.) character matches new-line characters. Note This modifier corresponds to the dotall property of the RegExp instance.
m — The caret (^) character and dollar sign ($) match before and after new-line characters. This modifier corresponds to the multiline property of the RegExp instance.
x — White space characters in the re string are ignored, so that you can write more readable constructors. This modifier corresponds to the extended property of the RegExp instance.

All other characters in the flags string are ignored.

Method Detail

exec

()

method

AS3 function exec(str:String):Object

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 9, AIR 1.0

Performs a search for the regular expression on the given string str.

If the g (global) flag is not set for the regular expression, then the search starts at the beginning of the string (at index position 0); the search ignores the lastIndex property of the regular expression.

If the g (global) flag is set for the regular expression, then the search starts at the index position specified by the lastIndex property of the regular expression. If the search matches a substring, the lastIndex property changes to match the position of the end of the match.

Parameters

str:String — The string to search.

Returns

Object — If there is no match, null; otherwise, an object with the following properties:

An array, in which element 0 contains the complete matching substring, and other elements of the array (1 through n) contain substrings that match parenthetical groups in the regular expression
index — The character position of the matched substring within the string
input — The string (str)

test

()

method

AS3 function test(str:String):Boolean

Language Version:

ActionScript 3.0

Runtime Versions:

Flash Player 9, AIR 1.0

Tests for the match of the regular expression in the given string str.

Parameters

str:String — The string to test.

Returns

Boolean — If there is a match, true; otherwise, false.

Example ( How to use this example )

The following example shows the use of the test() method on a regular expression in which the g (global) flag is set:

var re1:RegExp = /\w/g;
var str:String = "a b c";
trace (re1.lastIndex); // 0
trace (re1.test(str)); // true
trace (re1.lastIndex); // 1
trace (re1.test(str)); // true
trace (re1.lastIndex); // 3
trace (re1.test(str)); // true
trace (re1.lastIndex); // 5
trace (re1.test(str)); // false

Examples ( How to use this example )

RegExpExample.as

The following example shows how you can use regular expressions to parse strings and return a new string or a Boolean value, based on the string passed in. The informalizeGreeting() method simply replaces the word Hello with Hi, regardless of case. It also strips out the surname in the name in the string (assuming that name matches the specified pattern). In the validateEmail() and validatePhoneNumber() methods, the string passed is checked to see if its pattern matches a valid email address or a specific phone number pattern, and the methods return Boolean values based on the results.

package {
    import flash.display.Sprite;

    public class RegExpExample extends Sprite {        
        public function RegExpExample() {            
            var formalGreeting:String = "Hello, John Smith.";
            trace(informalizeGreeting(formalGreeting));    // Hi, John.

            var validEmail:String = "name@domain.com";
            trace(validateEmail(validEmail));        // true
            
            var invalidEmail:String = "foo";
            trace(validateEmail(invalidEmail));  // false
            
            var validPhoneNumber:String = "415-555-1212";
            trace(validatePhoneNumber(validPhoneNumber));    // true
            
            var invalidPhoneNumber:String = "312-867-530999";
            trace(validatePhoneNumber(invalidPhoneNumber));  // false
        }
        private function informalizeGreeting(str:String):String {
            var pattern:RegExp = new RegExp("hello, (\\w+) \\w+", "i");
            return str.replace(pattern, "Hi, $1");
        }
        private function validateEmail(str:String):Boolean {
            var pattern:RegExp = /(\w|[_.\-])+@((\w|-)+\.)+\w{2,4}+/;
            var result:Object = pattern.exec(str);
            if(result == null) {
                return false;
            }
            return true;
        }
        private function validatePhoneNumber(str:String):Boolean {
            var pattern:RegExp = /^\d{3}-\d{3}-\d{4}$/;
            var result:Object = pattern.exec(str);
            if(result == null) {
                return false;
            }
            return true;
        }
    }
}