Getting collection index in pseudo-class? (jquery 1.8+)

Question

I am trying to implement a pseudo-class (in jQuery 1.8.3). Here is the code:

(function($) { $.extend($.expr[':'], { group: $.expr.createPseudo(function(arg) { var index = 0; return function(element) { index += 1; var num = parseInt(arg, 10); if (isNaN(num)) { return false; } return (((index-1) % (num*2)) < num); } }) }); })(jQuery); 

The purpose of this selector is to apply style to "n" consecutive groups of elements and can be used to color every three lines of the body ("this") in an alternate color (with the class "alt" ")

 $(this).children(':visible').has('td').filter(':group(3)').addClass('alt') 

This works well for one person. But if I repeat a few todes (with "$ (" .. ") each" construct ", the index is not reset intermediate. This effect can be successfully achieved in jquery 1.6, as we naturally had (in the basic" functional parameters of the group ") the index inside the set:

 (function($) { $.extend($.expr[':'], { group: function(element, index, matches, set) { var num = parseInt(matches[3], 10); if (isNaN(num)) { return false; } return index % (num * 2) < num; } }); })(jQuery); 

How can we achieve the same effects in jquery 1.8?

Thanks so much for your ideas!

Answer 1

There is a createPositionalPseudo function in Sizzle , but it is not displayed. By duplicating this function, I really can use it, and it worked. I simplified this simply:

 $.extend($.expr[':'], { group: $.expr.createPseudo(function(arg){ return $.expr.createPseudo(function(seed, matches){ for (var i=0; i<seed.length; i++) if (i % (arg * 2) >= arg) matches.push(seed[i]); }) }) }); 

I am creating jsFiddle for testing.

I don’t know that inside Sizzle, it seems that seed is a list of elements for the pseudo-filter being processed, and matches is a list that is returned, indicating who passes the filter.

createPositionalPseudo also modifies seed , but the code above does not work. This can cause problems, since I do not know what is inside, I am not sure. However, it works well in my test.

JavaScript in jsFiddle contains create_group_pseudo_safe , it is not simplified. If there are any problems with simplified, this feature of the safe version should work.