When you are developing in SharePoint Online / Office 365 you will have to fetch appWebUrl and hostUrl if you want to perform any operation on your lists and libraries. I could find two ways of getting these values.
When you run your project it opens up the page Default.aspx. The URL of this page looks something like this.
Notice the query string parameters of SPAppWebUrl and SPHostUrl. You can fetch these values via a helper function.
1. Reading values of SPAppWebUrl and SPHostUrl from query string
When you run your project it opens up the page Default.aspx. The URL of this page looks something like this.
Notice the query string parameters of SPAppWebUrl and SPHostUrl. You can fetch these values via a helper function.