Sling Academy
Home/JavaScript/Creating Power-Aware Web Apps Using the Battery API in JavaScript

Creating Power-Aware Web Apps Using the Battery API in JavaScript

Last updated: December 12, 2024

With the growing ubiquity of mobile devices, developing web applications that are power-aware is crucial to enhance user experience. Excessive battery drain can lead to an unsatisfactory user experience, making it vital for developers to ensure applications are optimized for power consumption. One of the tools at your disposal as a developer is the Battery Status API. This handy API allows web applications to access battery status data, thereby aiding in creating applications that can adaptively adjust their functionality based on the device's current power status.

Understanding the Battery Status API

The Battery Status API provides the information necessary to modify your application's behavior according to the battery life of the device it is running on. The API lets you gather data on the battery's charge level, charging status, and estimated time for a full or empty charge. Here's a breakdown of how you can use it in your web application:

Checking Battery Status

Before utilizing the Battery Status API, check if your user's browser supports it. The API is accessible via the navigator object as navigator.getBattery(), which returns a promise that resolves to a battery manager object.

navigator.getBattery().then(function(battery) {
  console.log("Battery level: ", battery.level * 100 + "%");
  console.log("Is charging: ", battery.charging);
  console.log("Charging time remaining: ", battery.chargingTime + " seconds");
  console.log("Discharging time remaining: ", battery.dischargingTime + " seconds");
});

Using Battery Events

The battery status and charge state can also be dynamically monitored using several events provided by the API, such as onchargingchange, onlevelchange, onchargingtimechange, and ondischargingtimechange. You can create listeners for these events to respond in real-time to changes in the battery status.

navigator.getBattery().then(function(battery) {
  function updateAllBatteryInfo() {
    updateChargeInfo();
    updateLevelInfo();
    updateChargingTimeInfo();
    updateDischargingTimeInfo();
  }
  updateAllBatteryInfo();

  battery.addEventListener('chargingchange', function(){
    updateChargeInfo();
  });
  function updateChargeInfo(){
    console.log("Battery charging? " + (battery.charging ? "Yes" : "No"));
  }

  battery.addEventListener('levelchange', function(){
    updateLevelInfo();
  });
  function updateLevelInfo(){
    console.log("Battery level: " + battery.level * 100 + "%");
  }

  battery.addEventListener('chargingtimechange', function(){
    updateChargingTimeInfo();
  });
  function updateChargingTimeInfo(){
    console.log("Battery charging time: " + battery.chargingTime + " seconds");
  }

  battery.addEventListener('dischargingtimechange', function(){
    updateDischargingTimeInfo();
  });
  function updateDischargingTimeInfo(){
    console.log("Battery discharging time: " + battery.dischargingTime + " seconds");
  }
});

Creating a Power-Aware Application

To create a power-aware web app, consider implementing different functionalities based on the battery's status. For example, you could reduce the refresh rate of live content or defer resource-intensive tasks if the battery is low and not charging.

navigator.getBattery().then(function(battery) {
  if (!battery.charging && battery.level < 0.2) {
    console.log("Low battery. Reducing refresh rate to save power.");
    reduceRefreshRate();
  }

  battery.addEventListener('levelchange', function() {
    if (!battery.charging && battery.level < 0.2) {
      console.log("Battery level critical. Initiating power saving mode.");
      activatePowerSavingMode();
    }
  });

  function reduceRefreshRate() {
    // Code to reduce the refresh rate of the app
  }

  function activatePowerSavingMode() {
    // Code to activate power-saving mode
  }
});

Best Practices

While the Battery Status API can greatly enhance user experience by making your app more power-aware, it's important to use it considerately. Avoid unnecessary checks that may lead to polling. Also, consider user privacy and security implications before accessing the battery status.

Leveraging features like lazy loading of content, age-based caching strategies, and responsive animation settings can complement the usage of the Battery Status API to build efficient and sustainable web applications.

The industry is moving towards more efficient apps, and understanding the battery consumption patterns of your application can be a great step forward in providing a responsive and considerate user interface, ultimately leading to more satisfied users.

Next Article: Scheduling Non-Critical Tasks with JavaScript Background Tasks

Previous Article: Dynamic UI Adjustments for Energy Saving with the Battery API

Series: Web APIs – JavaScript Tutorials

JavaScript

You May Also Like

  • Handle Zoom and Scroll with the Visual Viewport API in JavaScript
  • Improve Security Posture Using JavaScript Trusted Types
  • Allow Seamless Device Switching Using JavaScript Remote Playback
  • Update Content Proactively with the JavaScript Push API
  • Simplify Tooltip and Dropdown Creation via JavaScript Popover API
  • Improve User Experience Through Performance Metrics in JavaScript
  • Coordinate Workers Using Channel Messaging in JavaScript
  • Exchange Data Between Iframes Using Channel Messaging in JavaScript
  • Manipulating Time Zones in JavaScript Without Libraries
  • Solving Simple Algebraic Equations Using JavaScript Math Functions
  • Emulating Traditional OOP Constructs with JavaScript Classes
  • Smoothing Out User Flows: Focus Management Techniques in JavaScript
  • Creating Dynamic Timers and Counters with JavaScript
  • Implement Old-School Data Fetching Using JavaScript XMLHttpRequest
  • Load Dynamic Content Without Reloading via XMLHttpRequest in JavaScript
  • Manage Error Handling and Timeouts Using XMLHttpRequest in JavaScript
  • Handle XML and JSON Responses via JavaScript XMLHttpRequest
  • Make AJAX Requests with XMLHttpRequest in JavaScript
  • Customize Subtitle Styling Using JavaScript WebVTT Integration