let startDate = new Date(); let elapsedTime = 0; const focus = function() { startDate = new Date(); }; const blur = function() { const endDate = new Date(); const spentTime = endDate.getTime() - startDate.getTime(); elapsedTime += spentTime; }; const beforeunload = function() { const endDate = new Date(); const spentTime = endDate.getTime() - startDate.getTime(); elapsedTime += spentTime; // elapsedTime contains the time spent on page in milliseconds }; window.addEventListener('focus', focus); window.addEventListener('blur', blur); window.addEventListener('beforeunload', beforeunload);
 
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