[рони]

fxobject,
мысли вслух ...

<div id="slider">

test

</div>
<script>
class RootElement {
	constructor(selector) {
		this.deviceCase = document.querySelector(selector);
        this.mousedown = this.fun.bind(this);
        this.deviceCase.addEventListener('mousedown',  this.mousedown)
	}

   fun(event) {
   alert([this.deviceCase.id, event.type]);
   this.deviceCase.removeEventListener('mousedown',  this.mousedown)
   }
}
new RootElement('#slider')
</script>