javascript - How to tell if browser/tab is active

Question

This question already has answers here:

Answer 1

In addition to Richard Sim?es answer you can also use the Page Visibility API.

if (!document.hidden) {
    // do what you need
}

This specification defines a means for site developers to programmatically determine the current visibility state of the page in order to develop power and CPU efficient web applications.

Learn more (2019 update)

• All modern browsers are supporting document.hidden
• http://davidwalsh.name/page-visibility
• https://developers.google.com/chrome/whitepapers/pagevisibility
• Example pausing a video when window/tab is hidden
  https://web.archive.org/web/20170609212707/http://www.samdutton.com/pageVisibility/