hello everybody;
up to what level can I use javascript (taking advantage of the strength of phonegap or Titanium) to create an android application.

ex 1:can I create or run a service (in the android sense) !!! ?? or can I access to the GSM properties like provide package android.telephony.gsm.

best regards.

javascript , html5 and cSS3 is not native android development. PhoneGap is now called Cordova and you can find their documentation here and for Titanium over here

i think you don't understand well my quation. I am talking about limitation of javascript to create mobile native apps.

ex:for me, untill now, i cannot find a way to lunch/create a service(like if i use android.app.Service) using javascript :-(

by the way cordova(phonegap)/Titanium is powerful tools to create native mobile apps when we want to accelerate development process of a mobile native apps using (js,html5,css3).

by the way cordova(phonegap)/Titanium is powerful tools to create native mobile apps

These tools are not native, they are cross platform, full stop.
Native mean Android written in Java or iOS writen in Objective C. Not bunch of html & JS or C#. They maybe useful for company that cannot or is not willing to invest in Android and iOS devs, however they will never be fast as native code and will always be behind with latest Android SDK.

ok, i have a different point of view, but this is not my subject, may be we discuss this in another thread :=).

so now up to what level can i use javascript to create android apps ?

Basically you can do most what Javascript can do for you.
There are something which native code is better, like 3D graphic, cryptography etc. and of course there are something you can't do, such as Image Capture, NFC or Android OpenAccessory, all of them need to be implemented natively since there is currently no way to do this in JavaScript.