I'm trying to add a custom attribute on my element using jquery :

$('.map-areas-div').rand(numElements).each(function(){

      $(this).attr('element_id',4);

});

But in the end, my elements doesn't have a element_id attribute.

PS, my html elements look like :

<div type=ground class=map-areas-div style=position: absolute; top: 900px; left: 720px; height: 40px; width: 90px;></div>

Thank you for help