JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://demo.omnigon.com/christian_bovine/showtime/js/jquery-jvectormap-1.1.1.min.js"></script>
<script src="http://demo.omnigon.com/christian_bovine/showtime/js/jquery.jvectormap-us.js"></script>
<div id="map"></div>

CSS

.jvectormap-label {
    position: absolute;
    display: none;
    border: solid 1px #CDCDCD;
    -webkit-border-radius: 3px;
    -moz-border-radius: 3px;
    border-radius: 3px;
    background: #292929;
    color: white;
    font-family: sans-serif, Verdana;
    font-size: smaller;
    padding: 3px;
}
.jvectormap-zoomin, .jvectormap-zoomout {
    position: absolute;
    left: 10px;
    -webkit-border-radius: 3px;
    -moz-border-radius: 3px;
    border-radius: 3px;
    background: #292929;
    padding: 3px;
    color: white;
    width: 10px;
    height: 10px;
    cursor: pointer;
    line-height: 10px;
    text-align: center;
}
.jvectormap-zoomin {
    top: 10px;
}
.jvectormap-zoomout {
    top: 30px;
}
#map {
    width: 100%;
    height: 500px;
}

JavaScript

$(function () {
           //assign markers to a variable
           var mapMarkers = [{
               latLng: [41.50, -87.37],
               name: 'Chicago',
               newvalue: '300'
           }, {
               latLng: [32.46, -96.46],
               name: 'Dallas',
               newvalue: '301'
           }, {
               latLng: [36.10, -115.12],
               name: 'Las Vegas',
               newvalue: '302'
           }, {
               latLng: [34.3, -118.15],
               name: 'Los Angeles',
               newvalue: '303'
           }, {
               latLng: [40.43, -74.00],
               name: 'New York City',
               newvalue: '304'
           }];

           $('#map').vectorMap({
               map: 'us_aea_en',
               zoomOnScroll: false,
               hoverOpacity: 0.7,
               markerStyle: {
                   initial: {
                       fill: '#F8E23B',
                       stroke: '#383f47'
                   }
               },
               markers: mapMarkers,
               onMarkerHover: function (event, index) {
                   var a = 2;
                   //retrieve marker by the index and parse the string value as an integer
                   var newval = parseInt(mapMarkers[index].newvalue);
                   var b = 2 + newval; //need to get the value from each markers and save the value to newval
                   alert(b);
               }
           });
       });