js获取手机重力感应api

 <html>
 <head>
     <title>DeviceOrientationEvent</title>
     <meta charset="UTF-8" />
 </head>
 <body>
 <p>左右：<span id="alpha">0</span></p>
 <p>前后：<span id="beta">0</span></p>
 <p>扭转：<span id="gamma">0</span></p>
 <p>指北针指向：<span id="heading">0</span>度</p>
 <p>指北针精度：<span id="accuracy">0</span>度</p>
 <script type="text/javascript">
     function orientationHandler(event) {
         document.getElementById("alpha").innerHTML = event.alpha;
         document.getElementById("beta").innerHTML = event.beta;
         document.getElementById("gamma").innerHTML = event.gamma;
         document.getElementById("heading").innerHTML = event.webkitCompassHeading;
         document.getElementById("accuracy").innerHTML = event.webkitCompassAccuracy;
     }

     if (window.DeviceOrientationEvent) {
         window.addEventListener("deviceorientation", orientationHandler, false);
     } else {
         document.body.innerHTML = "What user agent u r using???";
     }
 </script>
 </body>
 </html>