重力感应获取(摇一摇)

function sharkingFn(obj, callback) {
    if (window.DeviceMotionEvent) {
        window.addEventListener('devicemotion', deviceMotionHandler, false);
    }
    var SHAKE_THRESHOLD = 5000; // 灵敏度
    var last_update = 0;
    var x, y, z, last_x = 0, last_y = 0, last_z = 0;
    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) {
                callback();
            }
            last_x = x;
            last_y = y;
            last_z = z;
        }
    }
}