logic.js

let map;

async function initMap() {
    // The location of Uluru
    const position = { lat: -25.344, lng: 131.031 };
    // Request needed libraries.
    //@ts-ignore
    const { Map } = await google.maps.importLibrary("maps");
    const { AdvancedMarkerElement } = await google.maps.importLibrary("marker");

    // The map, centered at Uluru
    map = new Map(document.getElementById("map"), {
        zoom: 4,
        center: position,
        mapId: "DEMO_MAP_ID",
    });

    // The marker, positioned at Uluru
    const marker = new AdvancedMarkerElement({
        map: map,
        position: position,
        title: "Uluru",
    });
}

initMap();

function getDistanceFromLatLonInKm(lat1, lon1, lat2, lon2) {
    var R = 6371;
    var dLat = deg2rad(lat2 - lat1);
    var dLon = deg2rad(lon2 - lon1);
    var a =
        Math.sin(dLat / 2) * Math.sin(dLat / 2) +
        Math.cos(deg2rad(lat1)) *
        Math.cos(deg2rad(lat2)) *
        Math.sin(dLon / 2) *
        Math.sin(dLon / 2);
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    var d = R * c;
    return d;
}

function deg2rad(deg) {
    return deg * (Math.PI / 180);
}