> *Subject:* [qooxdoo-devel] javascript anomaly with regexp literal?
> *From:* "Derrell Lipman" <[EMAIL PROTECTED]>
> *To:* "qooxdoo Development" <qooxdoo-devel@lists.sourceforge.net>
> *Date:* Thu, 9 Oct 2008 12:36:13 -0400
>
> This seems odd and I can't find any documentation stating why it's
> so...
>
> This application has a function which tests a string for containing
> only digits. It uses a regular expression literal assigned to a
> local variable in a function. That regular expression, however,
> appears to be persistent across calls to the function.
There's a simpler case which exhibits behaviour that is unexpected:
var re1 = /\?/g;
re1.lastIndex;
0
re1.test("a?");
true
re1.lastIndex;
2
re1.test("a?aaa");
false
re1.lastIndex;
0
re1.test("a?");
true
re1.lastIndex;
2
"a?aa".replace(re1, "b");
"abaa"
re1.lastIndex;
0
This was collated from various tests in Firebug console. So calling test()
using a regular expression changes lastIndex to after the match position
(or resets it to 0 if no match), but calling replace() resets it to 0
before and after the replace action.
So you have to be careful using test() quite apart from the fact that the
same regular expression object is used when a regex literal is declared.
Hugh
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