ExtJS 4.2 - Possible causes of a “Sychronous XMLHttpRequest” warning?

Question

Good day, sorry for the seemingly broad question title.

I am building an ExtJS4 application using php and sql for the user data. Everything was going fine until one

Answer 1

I had this error a while a ago. It is caused by Ext.Loader which loads the Ext classes dynamically.

I could solve it by adding the required classes in the Ext.require([...]) statement in the main js file of my application (i.e. app.js).

The docs for Ext.Loader explain when and why asynchronous and synchronous loading happens.