Can't add a comment to the excellent explanation in the other post but wanted to mention that a great documentation source can be found here.
It is enough to register an event function for accelerometer like so:
if(window.DeviceMotionEvent){
window.addEventListener("devicemotion", motion, false);
}else{
console.log("DeviceMotionEvent is not supported");
}
with the handler:
function motion(event){
console.log("Accelerometer: "
+ event.accelerationIncludingGravity.x + ", "
+ event.accelerationIncludingGravity.y + ", "
+ event.accelerationIncludingGravity.z
);
}
And for magnetometer a following event handler has to be registered:
if(window.DeviceOrientationEvent){
window.addEventListener("deviceorientation", orientation, false);
}else{
console.log("DeviceOrientationEvent is not supported");
}
with a handler:
function orientation(event){
console.log("Magnetometer: "
+ event.alpha + ", "
+ event.beta + ", "
+ event.gamma
);
}
There are also fields specified in the motion event for a gyroscope but that does not seem to be universally supported (e.g. it didn't work on a Samsung Galaxy Note).
There is a simple working code on GitHub