我将如何计算点之间的距离谷歌地图Api V3

我正在做一个项目，它几乎已经完成了。问题是，我对Javascript还很陌生，不知道如何做一些可能很简单的事情。这是我的部分代码：

var dista;
var p;
var addrbounds;
var addrlat;
var addrlng;
var addr;
var icon = new google.maps.MarkerImage("http://maps.google.com/mapfiles/ms/micons/red.png",
new google.maps.Size(32, 32), new google.maps.Point(0, 0),
new google.maps.Point(16, 32));
var center = null;
var map = null;
var currentPopup;
var bounds = new google.maps.LatLngBounds();
function addMarker(lat, lng, info) {
var address = document.myform.customer.value;
var geocoder = new google.maps.Geocoder();
geocoder.geocode({address: address}, function(results, status) {
if (status == google.maps.GeocoderStatus.OK) {
var addrbounds = results[0].geometry.location; //get geocoded results into variable
var addrlat = results[0].geometry.location.lat();
var addrlng = results[0].geometry.location.lng();
var p = new google.maps.LatLng(addrlat, addrlng);
var pt1 = new google.maps.LatLng(lat, lng);
dista = pt1.distanceFrom(p); //calculate distance between the points
var di = (dista/1000);
document.myform1.memory.value = di; //add dist to memory text box
return;
} else {
alert(address + ' not found');
}
});
// desired spot for if statement regarding distance
var pt = new google.maps.LatLng(lat, lng);
bounds.extend(pt);
var marker = new google.maps.Marker({
position: pt,
icon: icon,
map: map
});
var popup = new google.maps.InfoWindow({
content: info,
maxWidth: 300
});
google.maps.event.addListener(marker, "click", function() {
if (currentPopup != null) {
currentPopup.close();
currentPopup = null;
}
popup.open(map, marker);
currentPopup = popup;
});
google.maps.event.addListener(popup, "closeclick", function() {
map.panTo(center);
currentPopup = null;
});
}

基本上，它的作用是在addMarker（）函数中发生的第一件事是对地址进行地理编码，然后计算与地址的距离。这很好用。当想要获得地理编码器的距离以创建if语句时，问题就来了，如果数据库在某个半径内，则只添加数据库中的标记。正如你所看到的，我试着把它移到一个文本框里。这似乎有效，但它是循环的一部分，不会随着循环的每次运行而更新。

我已经被困了几天了，如果有任何帮助，我们将不胜感激。我讨厌如此接近终点却被卡住！

编辑：

我开始工作了。我就是这样做的：

var dista;    
var p;
var addrbounds;
var addrlat;
var addrlng;
var icon = new google.maps.MarkerImage("http://maps.google.com/mapfiles/ms/micons/red.png",
new google.maps.Size(32, 32), new google.maps.Point(0, 0),
new google.maps.Point(16, 32));
var center = null;
var map = null;
var currentPopup;
var bounds = new google.maps.LatLngBounds();
function addMarker(lat, lng, info) {    
var address = document.myform.customer.value;
var geocoder = new google.maps.Geocoder();
geocoder.geocode({address: address}, function(results, status) {
  if (status == google.maps.GeocoderStatus.OK) {
  var addrbounds = results[0].geometry.location;
  var addrlat = results[0].geometry.location.lat();
  var addrlng = results[0].geometry.location.lng();
  var p = new google.maps.LatLng(addrlat, addrlng);
  var pt1 = new google.maps.LatLng(lat, lng);
  dista = pt1.distanceFrom(p);
  var di = (dista/1000);
  document.myform1.memory.value = di;
  document.myform1.memory1.value = addrlat;
  document.myform1.memory2.value = addrlng;
  return;
} else {
  alert(address + ' not found');
}
 });
var tstlat = document.myform1.memory1.value;
var tstlng = document.myform1.memory2.value;
var tstpt = new google.maps.LatLng(tstlat, tstlng);
var pt = new google.maps.LatLng(lat, lng);
var distan = pt.distanceFrom(tstpt);
var tstdistance = (distan/1000);
if (tstdistance < 20){
// alert (tstdistance);
bounds.extend(pt);
var marker = new google.maps.Marker({
position: pt,
icon: icon,
map: map
});
var popup = new google.maps.InfoWindow({
content: info,
maxWidth: 300
});
google.maps.event.addListener(marker, "click", function() {
if (currentPopup != null) {
currentPopup.close();
currentPopup = null;
}  
popup.open(map, marker);
currentPopup = popup;
});
google.maps.event.addListener(popup, "closeclick", function() {
map.panTo(center);
currentPopup = null;
});
}
else
 {
 return;
 }}

现在我只需要修复一个地图刷新问题，然后项目就完成了！