Detecting Browser Tab Focus for Optimized Resource Usage

When a webpage contains sensitive information or performs intensive operations that consume network resources, managing the focus of browser tabs becomes crucial. Detecting whether a particular tab is currently in focus allows you to implement strategies to optimize resource usage.

One reliable cross-browser method to determine if a tab has focus utilizes the window.onfocus and window.onblur event handlers. These events are triggered whenever a tab gains or loses focus, respectively.

In the context of your application that periodically polls for stock prices, you can implement the following strategy:

1. Define event handlers for window.onfocus and window.onblur:

   window.onfocus = function() {
     // Tab has gained focus
     console.log('Tab is in focus');
   };
   
   window.onblur = function() {
     // Tab has lost focus
     console.log('Tab is out of focus');
   };

2. Within the window.onfocus event handler, start or resume polling for stock prices:

   function startPolling() {
     // Start polling for stock prices
   }

3. Within the window.onblur event handler, stop polling for stock prices:

   function stopPolling() {
     // Stop polling for stock prices
   }

By implementing this approach, you effectively suspend polling operations when the tab is not in focus, conserving network resources and mitigating unnecessary traffic noise. When the tab regains focus, polling is automatically resumed, ensuring timely updates for the user.