Is there some programmatic way (or maybe a browser plugin) that allows users to arbitrarily run any jQuery they want on a webpage that is currently loaded in their browser?
Edit:
My motivation is to be able to test jQuery syntax and commands ahead of time on a page and then go add them to its source or suggest tweaks to the webadmins whose pages I experimented with.
I have been using jQuery from the main site to run the tests. It is currently on 3.5.1: jQuery download page
FireQuery is a great Firebug extension that can include jQuery for you and from there you´re able to use jQuery in your console.
"jQuerify: enables you to inject jQuery into any web page"