David Walsh Blog

5 More HTML5 APIs You Didn’t Know Existed

The HTML5 revolution has provided us some awesome JavaScript and HTML APIs.  Some are APIs we knew we’ve needed for years, others are cutting edge mobile and desktop helpers.  Regardless of API strength or purpose, anything to help us better do our job is a step in the right direction.  I recently shared with you 5 HTML5 APIs You Didn’t Know Existed in the hope that some of them would inspire you to improve your own web apps.  I’d like to share with you 5 more lessor known HTML5 APIs — hopefully you find some of them useful!

Fullscreen API

The awesome Fullscreen API allows developers to programmatically launch the browser into fullscreen mode, pending user approval:

// Find the right method, call on correct element
function launchFullScreen(element) {
  if(element.requestFullScreen) {
  } else if(element.mozRequestFullScreen) {
  } else if(element.webkitRequestFullScreen) {

// Launch fullscreen for browsers that support it!
launchFullScreen(document.documentElement); // the whole page
launchFullScreen(document.getElementById("videoElement")); // any individual element

Any element can be pushed to fullscreen, and there’s even a CSS pseudo-class to allow some control over the screen while in fullscreen mode.  This API is especially useful for JavaScript game development;  especially first person shooters like BananaBread!

Page Visibility API

The Page Visibility API provides developers an event to listen in on, telling developers when the user focuses on a page’s tab, and also when the user moves to another tab or window:

// Adapted slightly from Sam Dutton
// Set name of hidden property and visibility change event
// since some browsers only offer vendor-prefixed support
var hidden, state, visibilityChange; 
if (typeof document.hidden !== "undefined") {
  hidden = "hidden";
  visibilityChange = "visibilitychange";
  state = "visibilityState";
} else if (typeof document.mozHidden !== "undefined") {
  hidden = "mozHidden";
  visibilityChange = "mozvisibilitychange";
  state = "mozVisibilityState";
} else if (typeof document.msHidden !== "undefined") {
  hidden = "msHidden";
  visibilityChange = "msvisibilitychange";
  state = "msVisibilityState";
} else if (typeof document.webkitHidden !== "undefined") {
  hidden = "webkitHidden";
  visibilityChange = "webkitvisibilitychange";
  state = "webkitVisibilityState";

// Add a listener that constantly changes the title
document.addEventListener(visibilityChange, function(e) {
  // Start or stop processing depending on state

}, false);

When used properly, a developer can avoid expensive tasks (like AJAX polling or animating) when the tab isn’t in focus.

getUserMedia API

The getUserMedia API is incredibly interesting;  this API provides access to device media, like your MacBook’s camera!  Using this API, the <video> tag, and canvas, you can take beautiful photos within your browser!

// Put event listeners into place
window.addEventListener("DOMContentLoaded", function() {
  // Grab elements, create settings, etc.
  var canvas = document.getElementById("canvas"),
    context = canvas.getContext("2d"),
    video = document.getElementById("video"),
    videoObj = { "video": true },
    errBack = function(error) {
      console.log("Video capture error: ", error.code); 

  // Put video listeners into place
  if(navigator.getUserMedia) { // Standard
    navigator.getUserMedia(videoObj, function(stream) {
      video.src = stream;
    }, errBack);
  } else if(navigator.webkitGetUserMedia) { // WebKit-prefixed
    navigator.webkitGetUserMedia(videoObj, function(stream){
      video.src = window.webkitURL.createObjectURL(stream);
    }, errBack);
}, false);

Look forward to using this API quite a bit in the future — interactivity within the browser will be the norm a year from now!

Battery API

The Battery API has been updated; read JavaScript Battery API Update to see the new code pattern!

The Battery API is obviously a mobile-targeted API providing insight into the device’s battery level and status:

// Get the battery!
var battery = navigator.battery || navigator.webkitBattery || navigator.mozBattery;

// A few useful battery properties
console.warn("Battery charging: ", battery.charging); // true
console.warn("Battery level: ", battery.level); // 0.58
console.warn("Battery discharging time: ", battery.dischargingTime);

// Add a few event listeners
battery.addEventListener("chargingchange", function(e) {
  console.warn("Battery charge change: ", battery.charging);
}, false);

Knowing battery API and status can signal to the web application not to use battery-intensive processes and the like.  Not a groundbreaking API but surely a helpful one.

Link Prefetching

Link prefetching allows developers to silently preload site contents to project a more fluid, seamless web experience:

<!-- full page -->
<link rel="prefetch" href="https://davidwalsh.name/css-enhancements-user-experience" />

<!-- just an image -->
<link rel="prefetch" href="https://davidwalsh.name/wp-content/themes/walshbook3/images/sprite.png" />

There’s five more HTML5 APIs to research and tinker with.  Keep in mind that these APIs will be used widely in a few years, so the sooner you get acquainted with them, the better you’ll be equipped to create world-class web applications.  Take a few moments to explore these APIs and see what you can put together!