I am facing a javascript error in IE7 when trying to embed google map on a page. Firefox and Opera are displaying the map properly, but not IE7 which instead gives the following error:

Line: 19
Char: 2
Error: Object doesn't support this property or method.
HTML Code:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Strict//EN">
<html>
<head>
<title>Map</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<script src="http://maps.google.com/maps?file=api&amp;v=2&amp;key=ABQIAAAAUrvJiGLiw9De7R0N_2_bjBQWRJvwqkqS2safuwRocnXIIkx4WhS6E2SAkFKzcx19P9i4zLbNSNDjZw" type="text/javascript"></script>  

<script type="text/javascript">

var map;
var gmarker = {};
var targets = {};

function init_map() {
	map = new GMap2(document.getElementById('map'));
	map.addControl(new GSmallZoomControl());

	var lats = items.map(function(info) { return info.lat }).sort(function(a,b){return a - b});
	var lngs = items.map(function(info) { return info.lng }).sort(function(a,b){return a - b});
	var l = lats.length;
	var s = lats[Math.round((l-1) * 0)];
	var w = lngs[Math.round((l-1) * 0)];
	var n = lats[Math.round((l-1) * 0.90)];
	var e = lngs[Math.round((l-1) * 0.90)];
	var pad = 0;

	bounds = new GLatLngBounds(
		new GLatLng(s,w),
		new GLatLng(n,e)
	);
	map.setCenter(
		bounds.getCenter(),
		map.getBoundsZoomLevel(bounds)
	);
	for(i=0; i < items.length; i++) {
		var target = items[i];
		addMarker(target);
	}
}

window.onload = init_map;
window.onunload = GUnload;

function addMarker(target) {
	var marker = new GMarker(new GLatLng(target.lat, target.lng));
	GEvent.addListener(marker, 'click',
		function() { marker.openInfoWindowHtml(target.html); } 
	);  
	map.addOverlay(marker);

	gmarker[target.id] = marker;
	targets[target.id] = target;
}

function selectLocation(i) {
	var marker = gmarker[i];
	var target = targets[i];
	map.panTo(new GLatLng(target.lat, target.lng));
	marker.openInfoWindowHtml(target.html);
}

</script>

</head>

<body>

<script type="text/javascript">
var items = [
{
	id: 1,
	html: 'Location 1 Details Here',
	lng: 30.6,
	lat: 38.1
},
{
	id: 2,
	html: 'Location 2 Details Here',
	lng: 30.5,
	lat: 38.2
},
{
	id: 3,
	html: 'Location 3 Details Here',
	lng: 30.7,
	lat: 38.2
}
]
</script>

<div id="map" style="width: 350px; height: 300px;"></div>

</body>
</html>
Apparently, these lines are causing the problem:
HTML Code:
	var lats = items.map(function(info) { return info.lat }).sort(function(a,b){return a - b});
	var lngs = items.map(function(info) { return info.lng }).sort(function(a,b){return a - b});
but I am not sure what an IE7 fix would look like, if you have any suggestions please let me know, thanks!