JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://maps.google.com/maps/api/js?sensor=false" 
type="text/javascript"></script>

<div id='map-container'>
    <div id="map"  style="width:1000px; height:1000px"></div>
</div>


<script type="text/javascript">
    
    var barn = new google.maps.LatLng(52.6904, -3.3392);
    
    var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 9,
    center: barn,
    mapTypeId: google.maps.MapTypeId.TERRAIN,
    panControl: false,
    scrollwheel: false,
    zoomControl: true,
    mapTypeControl: false,
    });
    
    /* =========================THINGS TO DO========================= */
    // Pistyll Rhaeadr,  The highest waterfall in Wales.
    var pistyll = new google.maps.LatLng(52.860, -3.376);
    // Dolanog (paddling)
    var dolanog = new google.maps.LatLng(52.698, -3.366);
    // Glyndwr Way (National Trail)
    var glyndwr = new google.maps.LatLng(52.660, -3.147);
    // Offas Dike
    var offas = new google.maps.LatLng(52.3444, -3.0509);
    
    var markers = [];
    
    markers[0] = new google.maps.Marker({
    position: pistyll,
    url: '#test1',
    title: 'Estados Unidos',
    map: map
    });
    
    markers[1] = new google.maps.Marker({
    position: dolanog,
    url: 'http://www.jaygeorge.co.uk/cv',
    title: 'Brasil',
    map: map
    });
    
    markers[2] = new google.maps.Marker({
    position: glyndwr,
    url: '#test1',
    title: '',
    map: map
    });
    
    markers[3] = new google.maps.Marker({
    position: offas,
    url: '#test1',
    title: 'Argentina',
    map: map
    });
    
    
    for ( i = 0; i < markers.length; i++ ) {
    google.maps.event.addListener(markers[i], 'click', function() {
    window.location.href = this.url;  //changed from markers[i] to this[i]
    });
    }
    
    
    </script>