Question on RegExp exec() method

jackhsu · December 17th, 2006, 11:22 PM

On page 195, after execute the following code

Code:

var sToMatch = "a bat, a Cat, a fAt baT, a faT cat";
var reAt = /at/gi;
var arrMatches = reAt.exec(sToMatch);

you said we get an array contains all the instances of "at" with indexes from 0 to 5. However I tested the code both in Firefox and IE7 and found I couldn't get the value from 1 to 5.

After I read instructions from O'Relly Javascript Reference , I get that the return array contains only index, input and [0] propreties. [1]...[n] is the String of the results of [parenthesized component matches. So with no parenthesized component I only get [0], while a subsequent call to reAt.exec(sToMatch);will continue the search and get the next "at".

nzakas · December 17th, 2006, 11:49 PM

While I'm not sure of your question, this is an error. The example should be:

Code:

var sToMatch = "a bat, a Cat, a fAt baT, a faT cat";
var reAt = /at/gi;
var arrMatches = sToMatch.match(reAt);

You are right, the exec() method returns an object representing the first match.

Nicholas C. Zakas
Author, Professional JavaScript for Web Developers (ISBN 0764579088)
http://www.nczonline.net/

javatogo · June 7th, 2007, 01:19 AM

followd by your code , only one index can be found
a poor method about do exec() like this:
    var sToMatch = "a bat, a Cat, a fAt baT, a faT cat";
    var reAt = /at/gi;
    var a0 = reAt.exec(sToMatch);
    var a1 = reAt.exec(sToMatch);
    var a2 = reAt.exec(sToMatch);
    var a3 = reAt.exec(sToMatch);
    var a4 = reAt.exec(sToMatch);
    var a5 = reAt.exec(sToMatch);
    var a6 = reAt.exec(sToMatch);
    alert(a0 + a1 + a2 + a3 + a4 + a5 + a6);

but the description from JS Reference 1.5 is :
exec :
Executes the search for a match in a specified string. Returns a result array.