A sample of how to subscribe your facebook app to users page via Facebook Javascript Web SDK
- Make sure to have facebook login in your facebook app
- Add Web Platform in your facebook app
- Setup the domain of you app
- Setup the web platform Site URL
- Set the app id in app.js
- Run the app under the app domain
PS:
- For development purposes, you can set in your hosts file a domains like "local.host", and use this as the app domain, or you can use ngrok
- You need to have manage_pages permission approved by facebook for other users besides app admin subscribe to their pages