Hacking Google Maps and Google Earth (ExtremeTech)

170 Part III — Google Map Hacks

script that provides an interface to the database. The CGI script is asked for a list of cities,

which it collects from the database and returns as XML, placing the name of each city into a

suitable attribute in an appropriate tag.

Listing 9-15 shows the showcitylist()function. This function is responsible for connect-

ing to the CGI script, requesting a list of cities, and formatting that list of cities as a list of

clickable links that will in turn trigger the loading of restaurants in a city.

Listing 9-15: Showing a List of Cities

function showcitylist() {

map.clearOverlays();

index = 0;

points = [];

markers = [];

markerinfo = [];

cities = []; message.innerHTML = ‘Select a City’;

infopanel.innerHTML = ‘’;

var request = GXmlHttp.create();

request.open(‘GET’,’/examples/ch09-16.cgi?m=citylist’, true);

request.onreadystatechange = function() {

if (request.readyState == 4) {

var xmlsource = request.responseXML;

var citylist = ;

xmlsource.documentElement.getElementsByTagName(“city”);

for (var i=0;i < citylist.length;i++) {

cities.push(citylist[i].getAttribute(“cityname”));

infopanel.innerHTML = infopanel.innerHTML +

‘<a href=”#” onClick=”loadcity(‘ +

i +

‘);”>’ +

citylist[i].getAttribute(“cityname”) +

‘</a><br/>’;

}

}

}

request.send(null);

}

Although when the script is initially executed all of the global variables will effectively be empty,

the showcitylist()function can also be called once a list of restaurants in a given city have

been listed, effectively resetting the application. The first step therefore is to reset the contents of

all the variables. You then format the HTML information window with a list of available cities by

loading the data from the CGI script as XML and creating a list of suitable links.

When the user clicks an individual city, the loadcity()function is triggered (see Listing

9-16). On the whole, this function is almost identical to the previous examples in this chapter;

it asks the CGI script for a list of restaurants in a given city.