index.js

function updatemap() {
    console.log("Updating map with realtime data")
    fetch("/data.json")
        .then(response => response.json())
        .then(rsp => {
            console.log(rsp.data)
            rsp.data.forEach(element => {
                latitude= element.latitude;
                longitude = element.longitude;

                cases=element.confirmed;
                if(cases>255){
                    color="rgb(255, 0, 0)";
                }
                else{
                    color="rgb(${cases},0,0)"
                }
                new mapboxgl.Marker({
                    draggable: false,
                    color:color
                })
                    .setLngLat([longitude, latitude])
                    .addTo(map);
            })
        })
}
let interval=20000;
setInterval(updatemap,interval);
//updatemap();