add functions to javascript / JQuery object -

$(".box").each(function(){     $(this).distance_left = function() {         return $(this).offset().left - $(this).parent().offset().left;     }     $(this).distance_top = function() {         return $(this).offset().top - $(this).parent().offset().top;     }  }); 

when call distance_left or distance_top on .box object, box.distance_left not function. why?

you need extend prototype:

$.fn.distance_left = function() { return -1; }; 

and can use on jquery objects:

$('#myid').distance_left(); // -1 

anyway particually case can use

$(this).position().left; $(this).position().top;