Google Maps API 3

CHAPTER 2 ■ TRANSFERRING FROM VERSION 2 TO 3
Time for code to run
Synchronous method calls
methodA is executed
methodB is executed
Asynchronous method calls
methodA is executed
methodB is executed
Figure 2-1. The difference between synchronous and asynchronous method calls
In the asynchronous method call, methodB doesn’t have to wait for methodA to finish. This is great
because you get better performance, but it also means that you can’t rely on a method call to be finished
when you invoke another method later in the code. This behavior has consequences in how you use v3.
In some cases, you need to check whether an object is properly initialized before you can interact with it,
whereas in v2 you didn’t have to do this because it all happened sequentially.
One example of this is when you need to access the bounds of the map. You can’t just call the
getBounds() method of the Map object after you’ve initialized the map, because at that point the map
isn’t ready and it doesn’t have any bounds. Instead, you have to listen to the bounds_changed event
before trying to grab it. The bounds_changed event fires whenever the bounds of the map have changed.
One of those occurrences is when the map has loaded. It also occurs whenever you pan or zoom
the map.
google.maps.event.addListener(map, 'bounds_changed', function() {
var bounds = map.getBounds();
});
Converting from Version 2 to 3
In this section, you will learn how to perform basic tasks such as creating a map and adding markers and
also compare how these tasks are done in v2 vs. v3.
Adding a Reference to the API
The most significant change here is that you no longer need an API key. This is really convenient since
you don’t have to create a new API key for every domain that you want to use Google Maps on.
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