JS 手机摇动

var SHAKE_THRESHOLD = 800;//摇动强度
var lastUpdate = 0;
var x, y, z, last_x, last_y, last_z;
var canshake = false;
function deviceMotionHandler(eventData) {
    var acceleration = eventData.accelerationIncludingGravity;
    var curTime = new Date().getTime();
    if ((curTime - lastUpdate) > 100) {
        var diffTime = (curTime - lastUpdate);
        lastUpdate = 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 (canshake && speed > SHAKE_THRESHOLD) {
            canshake = false;
            //DO STH
　　　　　　　if (window.DeviceMotionEvent) { window.removeEventListener('devicemotion', deviceMotionHandler, false); }
        }
        last_x = x;
        last_y = y;
        last_z = z;
    }
}