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HTML5 and JavaScript Web Apps

Cover of HTML5 and JavaScript Web Apps by Wesley Hales Published by O'Reilly Media, Inc.
  1. HTML5 and JavaScript Web Apps
  2. Preface
    1. Who This Book Is For
    2. Who This Book Is Not For
    3. What You’ll Learn
    4. About the Code
    5. Conventions Used in This Book
    6. Using Code Examples
    7. Safari® Books Online
    8. How to Contact Us
    9. Acknowledgments
  3. 1. Client-Side Architecture
    1. Before HTML5
    2. More Code on the Client
    3. The Browser as a Platform
    4. Conclusion
  4. 2. The Mobile Web
    1. Mobile First
    2. Deciding What to Support
      1. Mobile Web Browsers
    3. Mobile Browser Market Share
    4. Browser Grading
    5. HTML5 in the Enterprise
      1. Graceful Degradation
    6. QA and Device Testing
  5. 3. Building for the Mobile Web
    1. Mobile Web Look and Feel
      1. The Look
      2. The Feel
    2. Interactions and Transitions
      1. Sliding
      2. Flipping
      3. Rotating
      4. Debugging Hardware Acceleration
      5. Memory Consumption
    3. Fetching and Caching
    4. Network Type Detection and Handling
    5. Frameworks and Approaches
      1. Single Page
      2. No Page Structure
      3. 100% JavaScript Driven
      4. Mobile Debugging
  6. 4. The Desktop Web
    1. The Browser as a Platform
      1. Client Versus Server HTML Generation
    2. Device and Feature Detection
      1. Client-Side Feature Detection
      2. Client-Side userAgent Detection
      3. Server-Side userAgent Detection
    3. Compression
      1. GZIP Versus DEFLATE
      2. Minification
    4. JavaScript MVC Frameworks and the Server
      1. The Top Five Frameworks
      2. Backbone
      3. Ember
      4. Angular
      5. Batman
      6. Knockout
  7. 5. WebSockets
    1. Building the Stack
      1. On the Server, Behind the Scenes
    2. Programming Models
      1. Relaying Events from the Server to the Browser
      2. Binary Data Over WebSockets
      3. Managing Proxies
      4. Frameworks
  8. 6. Optimizing with Web Storage
    1. The Storage API
    2. The StorageEvent API
      1. What’s Racy and What’s Not?
    3. Using JSON to Encode and Decode
    4. Security and Private Browsing
      1. Security
      2. Private Browsing
    5. Who’s Using Web Storage?
      1. Using Web Storage Today
    6. Syncing Data from the Client Side
      1. Database Syncing with Backbone
    7. Using Web Storage in Any Browser
    8. Frameworks
      1. LawnChair
      2. persistence.js
  9. 7. Geolocation
    1. A Practical Use Case: User Tracking
    2. A Practical Use Case: Reverse Geocoding
    3. Frameworks
      1. geo-location-javascript
      2. Webshims lib
  10. 8. Device Orientation API
    1. A Practical Use Case: Scrolling with Device Movement
  11. 9. Web Workers
    1. A Practical Use Case: Pooling and Parallelizing Jobs
      1. Other Uses
  12. Index
  13. About the Author
  14. Colophon
  15. Copyright

Chapter 8. Device Orientation API

Accelerometers, gyroscopes, and compasses are now commonplace in mobile devices and laptops. With the Device Orientation API, you can capture movements at an extremely fine-grained level, receiving exact details on the motion and acceleration of the device.

Conceptually, an accelerometer behaves as a damped mass on a spring. When the accelerometer experiences an acceleration, the mass is displaced to the point that the spring is able to accelerate the mass at the same rate as the casing. The displacement is then measured to give the acceleration.

With applications ranging from military-based inertial guidance systems to tracking animals to measuring earthquakes and aftershocks, orientation hardware has been in use for quite some time. Now you have the opportunity to add this functionality to your applications to enhance how devices are tracked and interact with your user interface. It’s time to move beyond using the Device Orientation API only for games and simple Geolocation.

To begin, you need to understand the basics of the API and handling the measurements in JavaScript. The first DOM event provided by the specification, deviceorientation, supplies the physical orientation of the device, expressed as a series of rotations from a local coordinate frame. Here’s a simple check to see if this browser supports the DeviceOrientationEvent object:

supports_orientation : function() {
  try {
  return 'DeviceOrientationEvent' in
  window && window['DeviceOrientationEvent' ...

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