1window.onload = function () {
2
3  // Check if is IOS 13 when page loads.
4  if ( window.DeviceMotionEvent && typeof window.DeviceMotionEvent.requestPermission === 'function' ){
5
6      // Everything here is just a lazy banner. You can do the banner your way.
7      const banner = document.createElement('div')
8      banner.innerHTML = `<div style="z-index: 1; position: absolute; width: 100%; background-color:#000; color: #fff"><p style="padding: 10px">Click here to enable DeviceMotion</p></div>`
9      banner.onclick = ClickRequestDeviceMotionEvent // You NEED to bind the function into a onClick event. An artificial 'onClick' will NOT work.
10      document.querySelector('body').appendChild(banner)
11  }
12}
13
14
15function ClickRequestDeviceMotionEvent () {
16  window.DeviceMotionEvent.requestPermission()
17    .then(response => {
18      if (response === 'granted') {
19        window.addEventListener('devicemotion',
20          () => { console.log('DeviceMotion permissions granted.') },
21          (e) => { throw e }
22      )} else {
23        console.log('DeviceMotion permissions not granted.')
24      }
25    })
26    .catch(e => {
27      console.error(e)
28    })
29}