javascript - How to tell if the user has switched to the current tab?

Question

I noticed that YouTube will only start playing the video when the user switches to the current tab.
So when a user opens multiple tabs, how to determine whether the user has switched to the current tab?

Answer 1

There is a Page Visibility API, you can take a look

I have thought about this implementation before, but it actually has shortcomings. What if sometimes I just want to listen to the sound? (:evil

Answer 2

document.addEventListener('visibilitychange', function() {
    if (!document.hidden) {
        // code
    }
})