Javascript。 检查是否没有焦点标签

Question

Now i'm using visibilitychange event to see which browser tab is active. I use active tab to watch some events on server side, and I don't want to run this watcher in all open tabs.

But now I want to run this watcher even if no tab is in focus, but still, in just one tab.

How to check if no tab is in focus and ensure that some script is running in only one background tab?

Answer 1

You have to solve the issue of communicating between tabs. There are several options:

1. Cookies
2. Local storage
3. Server side syncing (WebSockets, Ajax pooling, etc)

Each tab will have to update its state in the shared data centre (one of the above).

Once that is done, you should use a master selecting algorithm to decide which one of the tab should communicate with the server. In your case, this could be as simple as the first opened tab.

There are some quirks when using local storage such as two different sub-domains can't access the same local storage. Cookies are another way around where you can define parent domain as well. I would say the third option is the best in terms of debugging and adding more complex selection logic.