Is it possible write same code run as web App and App ?
Not sure I completely understand what you mean, but yes, in principe you use the same code for a webapp that you use in an app. By using Phonegap / Cordova you use the same code to run inside a container that makes it look like it’s a native app.
it depends what application you build.
in my experience, if you build generap application/webapp, you just have to write HTML5 without hardware access.
I want reuse ionic’s components in a web app,may be next month we will build an ios app
As long as you do not use any cordova-related stuff, then you should be fine. But be aware that ionic is ment to be used together with cordova, so the team might add some dependencies later on. Disclaimer: I’m not a team member.