Directly animating height results in a jerky motion on some web pages.  However, combining a CSS transition with jQuery's slideUp() makes for a smooth disappearing act.
const slideFade = (elem) => {
   const fade = { opacity: 0, transition: 'opacity 400ms' };
   elem.css(fade).slideUp();
   };
slideFade($('#mySelector'));
Fiddle with the code:
https://jsfiddle.net/00Lodcqf/435

In some situations, a very quick 100 millisecond pause to allow more fading creates a slightly smoother experience:
   elem.css(fade).delay(100).slideUp();
This is the solution I used in the dna-engine project where you can view the code (github.com/dna-engine/dna-engine) for the dna.ui.slideFade() function to see additional support for toggling and callbacks.