Professional JavaScript | 15

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Professional JavaScript

Array Properties

Accessed as	After Call 1	After Call 2	Notes
results.index	1	4	Character position at which match occurred
results.input	965212234	965212234	The target string

Pattern Properties

Accessed as	After Call 1	After Call 2	Notes
reg.lastIndex	4	7	The index from which to begin the next search
reg.ignoreCase	false	false	Has the 'i' switch been used?
reg.global	true	true	Has the 'g' switch been used?
reg.source	(\d{2}2)	(\d{2}2)	The pattern being matched

Static Regular Expression Properties

Always referred to as properties of the generic RegExp object

Accessed as	After Call 1	After Call 2	Notes
RegExp. lastMatch	652	122	Last character sequence to match the pattern
RegExp. leftContext	9	9652	Characters to the left of the matching sequence
RegExp. rightContext	12234	34	Characters to the right of the matching sequence
RegExp.$1	652	122	See previous explanation
RegExp. LastParen	652	122	The last substring match to a parenthesized subexpression.

As you can see, exec() does a lot of behind the scenes work, especially if you're running Navigator.

Limitations of exec() in Internet Explorer

The JScript version of exec() is quite limited in comparison to that in JavaScript in two ways:

• It does not support the 'run-on' style of operation when the global flag is set.
• JScript regular expressions only have five properties as follows

RegExp.index, RegExp.input : Equivalent to results.index and results.input as above.

RegExp.lastIndex, reg.source: Equivalent to reg.lastIndex and reg.source as above

RegExp.$1: Equivalent to RegExp.$1 as above.

And so, with all that information behind us, we conclude our tour of regular expression support in JavaScript.

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