Issues with 3.0 when Loading App

Question

I'm not sure if this is a 3.0-specific problem or not, though I never saw the behavior prior to 3.0.

Sometimes (not always) when I load my app, the whole thing fails to load and I get a white screen.  If I click in the lower-left hand corner of IE I get an error message that 'esri' is undefined, leading me to think the call to load the API did not succeed properly (just a hunch though).

Was anything changed in terms of how the API loads itself when called between 2.8 and 3.0?

Sadly I can't access our app using Firefox due to corporate security restrictions but I do have access to Fiddler, if that will help someone identify the issue.

JK · Answer

That helps.  Thanks to both of you for your input.  I think I found the problem.

JohnGravois · Answer

The important thing to remember is that you have to make sure that no code makes calls to the esri namespace until after the page has loaded.  Since functions don't run until they are directed to run, this makes them a safe location.

As an example, "dojo.addOnLoad(init)" tells your application to fire the init function as soon as dojo indicates that the page is loaded.  calls to esri.* inside init will be fine.

JK · Answer

Yes.  So within the <head> tag I have my JavaScript.  So what you're saying in the JS anytime I reference esri.* it needs to reside within a JS function?  An example below is an esri.* reference in my JS code.  The  dojo.addOnLoad(init); is the last line of my JS and resides outside of a function.

var spatialRef = new esri.SpatialReference({wkid:102100});

As long as a reference like the line above is within a JS function{} I shouldn't get the 'esri' is undefined error when using /jsapi/arcgis/?v=3.x   ???
Are you referencing anything from the esri namespace outside of a function called by dojo.ready/addOnLoad? Due to the new way Dojo loads modules at 1.7, all references to esri.* need to be inside a function called once all modules. We should have had this in the migrating to 3.0 doc but missed it. It'll be there shortly.