JSFiddle - React, Tailwind, and code Playground

HTML

<div class="thing">
Click & drag this, releasing the mouse <b>below</b> this box. Then try to make it stop by clicking below.
</div>

<a href="#" id="stop">STOP</a>

CSS

.thing {
	padding:10px;
	width:200px;
	background:tomato;
	color:#fff;
}
body {
	font-family:sans-serif;
}

JavaScript

/* THIS ISNT WORKING */
$('#stop').on('click',function(){
	$('.draggable').off('mousemove');
	$('body').append('Im trying!');
});


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

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

        var $el = this;

        return $el.css('cursor', opt.cursor).on("mousedown", function(e) {
            var $drag = $(this).addClass('active-handle').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;
            $('.draggable').parents().on("mousemove", function(e) {				
                $('.draggable').offset({
                    left: e.pageX + pos_x - drg_w
                }).on("mouseup", function() {
                    $(this).removeClass('draggable');;
                });				
				e.stopPropagation();
            });
            e.preventDefault(); // disable selection
        });
		

    }
})(jQuery);
$('.thing').draggable();
$('#stop').one('click', function() {
	$('.thing').removeClass('draggable');
})