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Debugging common errors in ExtJs

If you check ExtJs form, you will find some issues commonly faced by developers. I have seen people spending hours to solve these issues without any clue.
Here is the list of few errors and expected root cause. Hope it will help someone. 


this.addEvents is not a function

Check instantiation of the class. Most probably you forgot to write “new” keyword while creating a class object.


namespace.MyClass is not a constructor

Check for typo in class definition or class instantiation.

Did you forget to include the js file in html page or in jsb configuration?


this.el is undefined / this.el is null

In ExtJs “el” variable hold the reference of DOM element. And DOM element only initialize, when UI render correctly on web browser. If you are getting this error,  then their is major chances of accessing “el” variable before UI component layout or render properly.


Component is appearing as gray out or it is hanging somewhere else

It can happen because of many other issue, but major reason is same id of two component. To resolve this issue, just use diff id for each component.



Some quick FAQ links

Grid FAQ

Form FAQ

TabPanel FAQ

Layout FAQ

Template FAQ


For more learning resources, you must go through highly recommended “Learn ExtJs” page. 

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