Regular Expression Objects

The regular expressions we've been using are actually treated as regular expression objects in JavaScript. There are two ways to create such objectsby just assigning a pattern to a variable (as we've been doing), or by explicitly creating a new regular expression object with the new operator:

 var regexp = /pattern/[modifiers]  var regexp = new RegExp("pattern",["modifiers"]) 

We've already seen that you can pass regular expression objects to methods such as match , or use the methods of such objects, such as exec . Let's take a more systematic look at regular expression objects now. You can find their properties and methods in Table 20.1 in overview, their properties in depth in Table 20.2, and their methods in overview in Table 20.3.

Table 20.1. The Properties and Methods of Regular Expression Objects

Properties	Methods
constructor	compile
global	exec
ignoreCase	test
lastIndex
multiline
source

Table 20.2. The Properties of Regular Expression Objects

Property	NS2	NS3	NS4	NS6	IE3a	IE3b	IE4	IE5	IE5.5	IE6
constructor			x	x			x		x	x
	Read-only
	This property specifies the function that creates an object.
global			x	x					x	x
	Read-only
	This property holds the Boolean setting of the g modifier.
ignoreCase			x	x					x	x
	Read-only
	This property holds the Boolean setting of the i modifier.
lastIndex			x	x					x	x
	Read/write
	This property holds the position where the next match begins in a searched string.
multiline			x	x					x	x
	Read-only
	This property holds a Boolean value indicating the state of the multiline modifier m used with a regular expression. The default is false .
source			x	x			x	x	x	x
	Read-only
	This property holds the text of the regular expression pattern itself.

Table 20.3. The Methods of Regular Expression Objects

Method	NS2	NS3	NS4	NS6	IE3a	IE3b	IE4	IE5	IE5.5	IE6
compile			x	x			x	x	x	x
	Returns: Regular expression object
	This method compiles a regular expression into an internal format for faster execution.
	Syntax: regexp .compile( pattern , [ modifiers ]) ; where pattern is the regular expression pattern, and modifiers are the modifiers you want to use (such as "ig").
exec			x	x			x	x	x	x
	Returns: Array of matches
	Returns an array of matches to a regular expression, or null if there were no matches. If you're using parentheses for matches, the first element in the array is the entire match, and the subsequent elements are the submatches to the sections of the regular expression enclosed in parentheses.
	Syntax: regexp .exec( string ) , where string is the text you want to work on. Note that the array returned by the exec method has three properties: input , index and lastIndex. The input property holds the searched string, the index property holds the position of the matched substring within the searched string, and the lastIndex property is the position following the last character in the match.
test			x	x			x	x	x	x
	Returns: Boolean
	Returns a Boolean value that indicates whether a pattern exists in a searched string.
	Syntax: regexp .test( string ) , where string is the text you want to search. Returns true if there was a match, false otherwise .