block2.js

const arrow = document.querySelector('.arrow');
const speed = document.querySelector('.speed-value ');

navigator.geolocation.watchPosition(data => {
    // successful retrieval
    speed.textContent = data.coords.speed;
    arrow.style.transform = `rotate(${data.coords.heading}deg)`;
}, (error) => {
    // unsuccessful retrieval
    console.error(error);
    alert('ENABLE GEOLOCATION!!!');
});