How to detect when a tab is focused or not in Chrome with Javascript? -

i need know if user viewing tab or not in google chrome. tried use events blur , focus binded window, blur seems working correctly.

window.addeventlistener('focus', function() {   document.title = 'focused'; });  window.addeventlistener('blur', function() {   document.title = 'not focused'; }); 

the focus event works weird, sometimes. if switch tab , back, focus event won't activate. if click on address bar , on page, will. or if switch program , chrome activate if tab focused.

2015 update: new html5 way visibility api (taken blowsie's comment):

document.addeventlistener('visibilitychange', function(){     document.title = document.hidden; // change tab text demo }) 

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the code original poster gives (in question) works, of 2011:

window.addeventlistener('focus', function() {     document.title = 'focused'; });  window.addeventlistener('blur', function() {     document.title = 'not focused'; }); 

edit: of few months later in chrome 14, still work, user must have interacted page clicking anywhere in window @ least once. merely scrolling , such insufficient make work. doing window.focus() not make work automatically either. if knows of workaround, please mention.