setCenter in google map api is not working. map is invisible - google-maps

Question

I have been working on Google map project and encountered this issue.
I wanted to use setCenter method to relocate map center. I only can see the gray map instead. I think it's supposed to be working find but I don't know what is wrong
Here is how it looks likeenter image description here
enter code here
var map;
var marker;
function initMap(){
var options = {
center: new google.maps.LatLng(37.4989885,127.03282719999993),
zoom : 8
};
map = new google.maps.Map(document.getElementById('map'), options);
marker = new google.maps.Marker({
position : {lat:37.4989885,lng:127.03282719999993},
map : map
});
}
function changePosition(altitude, longitude){
map.setCenter(new google.maps.LatLng(altitude,longitude));
marker.setPosition(new google.maps.LatLng(altitude,longitude));
}
$(function() {
var url = "tourXML";
$.ajax({
type : "GET",
url : url,
dataType : "text",
success : function(data) {
var temp = $.trim(data);
obj = JSON.parse(temp);
var longitude = parseFloat(obj.longitude);
var altitude = parseFloat(obj.altitude);
changePosition(altitude, longitude);
$("#altitude").html(obj.altitude);
$("#longitude").html(obj.longitude);
},
error : function() {
alert("error.");
}
});
});

Answer 1

You can use this code Modified it as per you need
map.setCenter(21.219381 ,72.840128);
or
map.setCenter(pos);
enter code here
function initMap ()
{
var map = new google.maps.Map(document.getElementById('map'), {
zoom: 5,
center: {lat: 21.219381, lng: 72.840128}
});
var geocoder = new google.maps.Geocoder;
var trafficLayer = new google.maps.TrafficLayer();
trafficLayer.setMap(map);
var infowindow = new google.maps.InfoWindow;
if (navigator.geolocation) {
navigator.geolocation.getCurrentPosition(function(position) {
var pos = {
lat: position.coords.latitude,
lng: position.coords.longitude
};
geocoder.geocode({'location': pos}, function(results, status) {
if (status === 'OK') {
if (results[0]) {
console.log(JSON.stringify(results[0]));
map.setZoom(11);
var marker = new google.maps.Marker({
position: pos,
map: map
});
infowindow.setContent(results[0].formatted_address);
infowindow.open(map, marker);
map.setCenter(pos);
} else {
window.alert('No results found');
}
} else {
window.alert('Geocoder failed due to: ' + status);
}
});
}, function() {
handleLocationError(true, infoWindow, map.getCenter());
});
} else {
// Browser doesn't support Geolocation
handleLocationError(false, infoWindow, map.getCenter());
}
}