Create a Simple App in SharePoint 2013 using Visual Studio 2012

Steps to create a SharePoint hosted app using visual studio 2012.

Open Visual Studio 2012

Create a new project -> Installed -> Templates -> SharePoint Apps -> App for SharePoint 2013 -> Enter name as "SampleApp"

Select site url and SharePoint-hosted app and finish it.

Open Scripts\App.js file, Add the code to meet your requirement

Click on Deploy the solution

Go to Site -> Site Contents -> SampleApp

Click on App to view the content on the App.