index.js

function initialize() {
    
	var geocoder = new google.maps.Geocoder();
	
	var mapOptions = {
		zoom: 8,
		mapTypeId: google.maps.MapTypeId.ROADMAP
	};
	
	var center = null;
	
	if (geocoder instanceof google.maps.Geocoder) {
		geocoder.geocode(
			{address: 'Oxford, United Kingdom'},
			function(results, status) {
				var result = results[0];
				if (status === 'OK') {
					center = result.geometry.location;
					if (center instanceof google.maps.LatLng) {
						mapOptions.center = center;
					}
				}
				
				var map = renderize(mapOptions);
				
				new google.maps.Marker({position: center, map: map});
			}
		);
	} else {
		renderize(mapOptions);
	}

}

function renderize(mapOptions) {
	return new google.maps.Map(document.getElementById('map-canvas'), mapOptions);
}

function loadScript() {
	var script = document.createElement('script');
	script.type = 'text/javascript';
	script.src = 'https://maps.googleapis.com/maps/api/js?v=3.exp&sensor=false&callback=initialize';
	document.body.appendChild(script);
}

window.onload = loadScript;