draggable div element with rxjs v6.3.2

rxjs-draggable.js

let draggableEl = document.querySelector('.draggable');

let mouseup$ = fromEvent(document, 'mouseup');
let mousemove$ = fromEvent(document, 'mousemove');
let mousedown$ = fromEvent(draggableEl, 'mousedown');

let mousedrag$ = mousedown$.pipe(
  mergeMap(({offsetX, offsetY}) =>
    mousemove$.pipe(
      map(({clientX, clientY}) => ({
        left: clientX - offsetX,
        top: clientY - offsetY,
      })),
      takeUntil(mouseup$),
    ),
  ),
);

mousedrag$.subscribe(({top, left}) => {
  draggableEl.style.top = top;
  draggableEl.style.left = left;
});