In Firefox you can right-click and Unload Tab which leaves the tab as one you can return to but unloads all the JS (including Service Workers) until you return to it. Firefox will auto-unload tabs as you open more tabs, but for sites like YouTube that do a lot of cross-tab chatter and have mega Service Workers trying to do background stuff (they don't need to) all of the time, it's nice to be able to Unload Tab directly from the right-click menu.