setInterval function fails when browser tab is inactive

Other Questions JavaScript
1

I am working with the following JavaScript code that initializes a timer. The function appears to function properly when the browser tab is active; however, when I switch to another tab and subsequently return, the timer does not display the correct time. Here’s a simplified version of the code I’m using. Additionally, I have attempted to use setTimeout, but ran into the same issue. One potential solution I considered is utilizing HTML5 Web Workers, but I am concerned about browser compatibility issues. Can anyone provide guidance on how to implement a setInterval that maintains correct timing even when the tab is not actively focused?

2

When browser tabs become inactive, the JavaScript timers such as setInterval and setTimeout may be throttled by the browser to enhance performance and battery life. This behavior can lead to inaccuracies in the timer's operation when you switch back to the tab.

To address this, consider using the Page Visibility API. This API allows you to detect when a page's visibility state changes and can help you manage your intervals more effectively. Here's an example of how you might implement this:

// Keep track of the timer also using Date.now()
let startTime = Date.now();
let elapsedTime = 0;
const interval = 1000; // 1 second

// Function to update the timer
function updateTimer() {
  elapsedTime = Date.now() - startTime;
  console.log("Elapsed Time: " + Math.floor(elapsedTime / 1000) + " seconds");
}

// Check for page visibility
function checkVisibility() {
  if (document.visibilityState === 'visible') {
    startTime = Date.now() - elapsedTime; // Adjust startTime keeping counted elapsed time
    requestAnimationFrame(tick);
  }
}

document.addEventListener('visibilitychange', checkVisibility);

function tick() {
  updateTimer();
  if (document.visibilityState === 'visible') { // Continue if tab is still active
    requestAnimationFrame(tick);
  }
}

// Initialize the first tick
requestAnimationFrame(tick);

In this implementation:

  • document.visibilityState determines if the page is visible or hidden.
  • We use requestAnimationFrame in place of setInterval for smoother and more consistent animations.
  • The visibilitychange event listener adjusts the start time so that the timer remains consistent.

This method does not rely on Web Workers, avoiding potential compatibility issues, and utilizes native browser capabilities to maintain more accurate timing.