js实现手机摇一摇

//手机摇一摇 ----------------------------------------------------------

init();
var SHAKE_THRESHOLD = 3000;
        var last_update = 0;
        var x = y = z = last_x = last_y = last_z = 0;
        function init() {
            if (window.DeviceMotionEvent) {
                window.addEventListener('devicemotion', deviceMotionHandler, false);
            } else {
                alert('not support mobile event');
            }
        }
        function deviceMotionHandler(eventData) {
            var acceleration = eventData.accelerationIncludingGravity;
            var curTime = new Date().getTime();
            if ((curTime - last_update) > 100) {
                var diffTime = curTime - last_update;
                last_update = curTime;
                x = acceleration.x;
                y = acceleration.y;
                z = acceleration.z;
                var speed = Math.abs(x + y + z - last_x - last_y - last_z) / diffTime * 10000;

if (speed > SHAKE_THRESHOLD) {
                    alert("摇动了");
                    media.setAttribute("src", "http://211.148.5.228:8002/Pages/test/Kalimba.mp3");
                    media.load();
                    media.play();  
                }
                last_x = x;
                last_y = y;
                last_z = z;
            }
        }