<div id="id_of_the_element" data-attribute_name="foo"></div>
var elem = document.getElementById("id_of_the_element");
var attribute_value = elem.getAttribute("data-attribute_name");
//OR with jquery...
var attribute_value = $('#id_of_the_element').attr('data-attribute_name');
//OR...
var attribute_value = $('#id_of_the_element').data('attribute_name');