script.js

const test = document.getElementById('test');
const test1 = document.getElementById('test1');
//test.textContent = "123124";

var mymap = L.map('mapid').setView([51.505, -0.09], 2);
L.tileLayer('https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token={accessToken}', {
    attribution: 'Map data &copy; <a href="https://www.openstreetmap.org/">OpenStreetMap</a> contributors, <a href="https://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, Imagery © <a href="https://www.mapbox.com/">Mapbox</a>',
    maxZoom: 18,
    id: 'mapbox.streets',
    accessToken: 'ADD MAPBOX ACCESS TOKEN HERE'
}).addTo(mymap);

marker1 = L.marker([51.505, -0.09]).addTo(mymap);
marker2 = L.marker([40.743720, -73.822030]).addTo(mymap);
marker3 = L.marker([39.760979, -84.192200]).addTo(mymap);

function testFunction() {
  mymap.closePopup();
  marker1.bindPopup("<b>Spiderman</b><br>New York, USA").openPopup();
}

function testFunction2() {
  mymap.closePopup();
  marker2.bindPopup("<b>Hulk</b><br>Ohio, USA").openPopup();
}

function testFunction3() {
  mymap.closePopup();
  marker3.bindPopup("<b>Wolverine</b><br>Cold Lake, Alberta, Canada").openPopup();
}