Improved version of Draggable without jQuery UI https://css-tricks.com/snippets/jquery/draggable-without-jquery-ui/

main.js

// bug - on each click this code creates a new event listener for all $drag parents
// serious lack of memory and permormance
// solution - unbind this event on 'mouseup' and make 'mouseup' once-executable via one()

(function($) {
    $.fn.drags = function(opt) {

        opt = $.extend({handle: '', cursor: 'move'}, opt);

        if(opt.handle === '') {
            var $el = this;
        } else {
            var $el = this.find(opt.handle);
        }

        return $el.css('cursor', opt.cursor).on('mousedown', function(e) {
            if(opt.handle === '') {
                var $drag = $(this).addClass('draggable');
            } else {
                var $drag = $(this).addClass('active-handle').parent().addClass('draggable');
            }
			
            var z_idx = $drag.css('z-index'),
                drg_h = $drag.outerHeight(),
                drg_w = $drag.outerWidth(),
                pos_y = $drag.offset().top + drg_h - e.pageY,
                pos_x = $drag.offset().left + drg_w - e.pageX;
				
            // bind first event
            // why parents() ?
            $drag.css('z-index', 1000).parents().on('mousemove.drags', function(e) {
                $('.draggable').offset({
                    top:e.pageY + pos_y - drg_h,
                    left:e.pageX + pos_x - drg_w
                }).one('mouseup', function() {
                    $(this).removeClass('draggable').css('z-index', z_idx);
                    
                    // unbind first event
                    $drag.parents().unbind('mousemove.drags');
                });
            });
            e.preventDefault(); // disable selection
			
        }).on('mouseup', function() {
            if(opt.handle === '') {
                $(this).removeClass('draggable');
            } else {
                $(this).removeClass('active-handle').parent().removeClass('draggable');
            }
        });

    }
})(jQuery);