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Run Tasks Only When Visible Using the Page Visibility API in JavaScript

Last updated: December 13, 2024

Web development often requires resource efficiency and enhancing the user experience. A feature that plays a significant role in achieving this is managing active operations based on the visibility state of a web page. Fortunately, the Page Visibility API in JavaScript provides a convenient way to determine and react to visibility changes, allowing us to suspend background operations when a page is not visible, thereby saving resources and enhancing performance.

By using the Page Visibility API, you can pause or defer unnecessary activity in inactive tabs, such as pausing video playback, stopping animations, or halting data fetching. In this article, you’ll learn how to implement the Page Visibility API and leverage it to run tasks only when a page is visible.

Understanding the Page Visibility API

The Page Visibility API offers a way to obtain the visibility state of a web page. It provides an event that signals visibility changes, and a property to check the current visibility status. These capabilities are accessible through:

  • document.hidden - A boolean that indicates if the page is currently hidden.
  • document.visibilityState - Returns the visibility state of the document, which can be 'visible', 'hidden', 'prerender', or 'unloaded'.
  • visibilitychange event - An event triggered in response to visibility state changes.

Basic Usage of the Page Visibility API

To use the Page Visibility API, you should listen for the visibilitychange event. Below is a simple example of how to handle visibility changes and execute a task only when the page is visible.

document.addEventListener('visibilitychange', function() {
  if (document.visibilityState === 'visible') {
    console.log('Page is visible, start or continue your task here.');
    // Start or continue a task
  } else {
    console.log('Page is hidden, pause or stop your task here.');
    // Pause or stop a task
  }
});

The code above listens for when the user switches back and forth between tabs or minimizes the browser. Based on the visibility change, you can control which operations continue to run or should be suspended.

Practical Applications

Using this approach can be applied in various real-world scenarios, helping in optimizing web applications. Here are some common cases where the Page Visibility API comes handy:

  • Multimedia Playbacks: Pausing video/audio when the tab is hidden and resuming once visible can preserve bandwidth and perform efficiently.
  • Data Fetching: You can pause periodic data fetching when the tab isn’t viewed and resume fetching to avoid unnecessary network requests.
  • Animation and Rendering tasks: Stop heavy computational tasks like animations that are not beneficial when the user is not viewing the tab.

Extended Example

Let's extend our earlier example to manage an imaginary application, which fetches updates from the server periodically:

let intervalId;

function startDataFetching() {
  intervalId = setInterval(() => {
    // Imagine fetchUpdates() as a function that fetches data
    console.log('Fetching updates from the server...');
    fetchUpdates();
  }, 5000); // Fetch every 5 seconds
}

function stopDataFetching() {
  clearInterval(intervalId);
  console.log('Stopped fetching updates.');
}

document.addEventListener('visibilitychange', function() {
  if (document.visibilityState === 'visible') {
    console.log('Page is visible, starting data fetching.');
    startDataFetching();
  } else {
    console.log('Page is hidden, stopping data fetching.');
    stopDataFetching();
  }
});

// Initial check in case the page started as visible
if (document.visibilityState === 'visible') {
  startDataFetching();
}

In this extended example, the interval will start fetching data every five seconds when the page is visible. If the window is minimized or the tab changed, the fetching process will be halted, and it will resume only when returning to the visible state.

Browser Support

The Page Visibility API is widely supported across modern browsers, including Chrome, Firefox, Safari, Edge, and Opera. It's crucial to ensure users can benefit from these optimizations, thus regular testing is recommended.

Conclusion

The Page Visibility API provides a fantastic approach to crafting efficient web applications by ensuring tasks run only when necessary. With this API, preserving both client and server-side resources becomes straightforward. Coupled with other performance optimization techniques, you can significantly boost user experience. Start implementing the Page Visibility API today to ensure your applications adapt to user engagement states efficiently.

Next Article: Pause Animations on Hidden Tabs via JavaScript Page Visibility

Previous Article: Detect Page Visibility Changes with the Page Visibility API in JavaScript

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