Anyboby help. Why function add class active this.parents(\".block-parent\").find(\".periods[data-period=\"+typelink+\"]\").addClass(\'active\')
work after second cl
It's because you're using this
var typelink = $(".block-head__link.active").attr("data-date")
to find the link you've just clicked on, and you haven't dealt with changing the classes yet so it's getting the previous element you gave the class active to. The following will return the correct data-date value of the clicked element, not one you think it might be that's saught by class name.
var typelink = $(this).data("date");
// var typelink = $(this).attr("data-date"); // this isn't how data is used
http://jsfiddle.net/kngU8/7/