Just look out for this not being supported and make sure your stuff still works. Eg, document.hidden might be undefined so don't initialize like this:

    doVisualUpdates = (document.hidden === true);

Well, you’d typically want to do visual updates when document.hidden wasn’t true, which would work fine.

He probably meant `(browser.hidden === false)` which wouldn't work if browser.hidden is undefined. Use == instead of === and it will work fine.

No, the opposite of that. If document.hidden === undefined, you don't want to use this optimization at all. What I was saying is, if you initialize doVisualUpdates as "document.hidden === true", in the case where it's undefined, you will never do visual updates.

`!document.hidden` would work, and it’s what most people would normally write already. `document.hidden == false` would not work; `false != undefined`.