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Static properties

reB.exec(sToMatch);

alert(reB.lastIndex); //outputs “1”

reB.lastIndex = 0;

reB.exec(sToMatch);

alert(reB.lastIndex); //outputs “1”

With the change in this code, both calls to

exec()

find the

in position 0, so both times, the alert dis-

plays

“1”

as the value of

lastIndex

Static properties

The static

RegExp

properties apply to all regular expressions in scope. These properties are also unique

because they each have two names: a verbose name and a short name beginning with a dollar sign. The

properties are listed in the following table.

Verbose Name

Short Name Description

input

The last string matched against (the string passed in

exec()

test()

)

lastMatch

The last matched characters

lastParen

The last matched group

leftContext

The substring before the last match

multiline

A Boolean value specifying whether all expressions

should use multiline mode

rightContext

$’

The substring after the last match

These properties can be used to tell you specific information about the match just completed using

exec()

test()

. Example:

var sToMatch = “this has been a short, short summer”;

var reShort = /(s)hort/g;

reS.test(sToMatch);

alert(RegExp.input); //outputs “this has been a short, short summer”

alert(RegExp.leftContext); //outputs “this has been a “

alert(RegExp.rightContext); //outputs “, short summer”

alert(RegExp.lastMatch); //outputs “short”

alert(RegExp.lastParen); //outputs “s”

This example illustrates how the various properties are used:

The

input

property is always equal to the string being tested.

RegExp.leftContext

contains everything before the first instance of

“short”

and

RegExp.rightContext

contains everything after the first instance of

“short”

The

lastMatch

property contains the last string that matches the entire regular expression,

which is

“short”

The

lastParen

property contains the last matched group, which in this case is

“s”

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