JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div id="mire"></div>
    <div id="mapdiv"></div>
    

    <script src="http://www.openlayers.org/api/OpenLayers.js"></script>
    <script>
function getGps(){
    var gps = map.getCenter()
                .transform(
                       new OpenLayers
                           .Projection('EPSG:900913'),
                       new OpenLayers
                           .Projection('EPSG:4326')
                      );

    $.getJSON(
        'http://open.mapquestapi.com/elevation/v1/profile?latLngCollection=' + gps.lat  + ',' + gps.lon,
        function(data) {
                gps = {
                    lon:gps.lon,
                    lat:gps.lat,
                    alt:data.elevationProfile[0].height
                }
               console.log(gps);
                $('#boutonGPS').attr('value', gps.lon+', '+gps.lat+' = '+gps.alt+'m');
        });
        markers.destroy();
                markers = new OpenLayers.Layer.Markers( "Markers" );
                map.addLayer(markers);
                markers.addMarker(new OpenLayers.Marker(gps));
        
    return gps;
}
    </script>
    <a href="http://leafletjs.com/examples/custom-icons.html">How to Change Marker Icon</a>
    <input id="boutonGPS" type="button" onclick="getGps();" value="get LonLat"></input>
</body>

CSS

#mapdiv { width:350px; height:350px; border:1px solid grey;opacity:.8;}
#mire { 
    margin-top:-197px;
    margin-left:157px;
    width:35px;
    height:35px;
    border:1px solid grey;
}
    div.olControlAttribution { bottom:3px; }

JavaScript

map = new OpenLayers.Map("mapdiv");
var mapnik = new OpenLayers.Layer.OSM();
map.addLayer(mapnik);

lonlat = new OpenLayers
                    .LonLat(0.30798, 44.45347)
                    .transform(
                        new OpenLayers.Projection("EPSG:4326"), // transform from WGS 1984
                        new OpenLayers.Projection("EPSG:900913") // to Spherical Mercator
                    );

var zoom = 12;

markers = new OpenLayers.Layer.Markers( "Markers" );
map.addLayer(markers);
markers.addMarker(new OpenLayers.Marker(lonlat));

map.setCenter(lonlat, zoom);