var map, zoom;
function initialize() {
var myLatLng = new google.maps.LatLng(38.8977, -77.0365);
zoom = 17;
var $map = document.getElementById("map");
map = new google.maps.Map($map, {
zoom: zoom,
center: myLatLng,
mapTypeId: google.maps.MapTypeId.ROADMAP,
scrollwheel: false,
disableDoubleClickZoom: true,
});
var marker = new google.maps.Marker({
position: myLatLng,
map: map
});
map.addListener('dblclick', function(e) {
zoomHandler(e.latLng, 1);
});
map.addListener('zoom_changed', function(e) {
setTimeout(function() {
zoom = map.getZoom();
}, 50);
});
$map.addEventListener('mousewheel', wheelEvent, true);
}
function wheelEvent(event) {
if (event.deltaY > 1)
zoomHandler(event, -1);
else
zoomHandler(event, 1);
}
function zoomHandler(event, zoomin) {
zoom += zoomin;
map.setZoom(zoom);
}
google.maps.event.addDomListener(window, 'load', initialize);
#map {
width: 100%;
height: 240px;
}
<div id="map"></div>
<script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyC9d3jaUX6Qdr0Uzvq6fQXVmZ1PBuHEVAQ"></script>