Detect when the sidebar has widgets

- [Instructor] To create these sidebar dependent layouts,…I first need to figure out a way of quickly testing…whether or not the sidebar is currently active.…If I got to any of my posts right now and scroll down,…you'll see here is a sidebar,…it's currently displaying on the bottom of the page…but there is definitely a sidebar here…and it has content.…The good news is we can ask WordPress whether or not…a specific sidebar or widgetized area currently…has widgets in it or not.…That's done using a function called is active sidebar.…Using that function, I want to be able to control my CSS…so I can provide one set of styles if we have a sidebar,…and another set of styles if we don't.…

To do that, I want to add an additional class…to the body element when we are on single posts.…Now if we go and inspect the code for the page,…you'll see the body element…has a ton of classes applied already.…Post template defaults, single, single post, post ID,…single format standard, da da da,…and there's a lot a lot of different information…