The ADAL library simplifies the process of obtaining and caching the authentication tokens required to retrieve data from Office 365. It is possible to avoid the ADAL library and handle this yourself, although I would recommend doing so as a learning exercise only.
I failed to find a simple example of how to achieve this, my search results often filled with examples of calling the APIs from server-side code or else utilising the Angular.js framework. This example is based on a more complex example.
The following snippet will log to the browser console the results of a call the to files endpoint of the Office 365 unified API, which will return a JSON object containing information about the files in the current users’ OD4B.
Register an Azure Active Directory App. Note that *every* Office 365 subscriptions comes with AAD and supports the creation of an app
Associate the required ‘permissions to other services’, in this case ‘Read users files’ via the Office 365 Unified API
Allow implicit flow
Not covered explicitly in the above article but also critical are the following steps:
Get the App’s Client ID and copy it into the snippet
Get the Azure Active Directory subscription ID and copy it into the snippet
Once the above steps have been completed, you can try out the snippet by embedding in a Script Editor web part, or you can run it externally to SharePoint as part of, say, a provider hosted app.
NOTE: I found that the call to files endpoint is failing for certain users. I am still unsure whether this is due to external vs internal users (is working for internal [.onmicrosoft.com] users) or whether it could be licencing issue. The /beta/me endpoint is working in all cases.
CORS: Cross-Origin Resource Sharing
ADAL: Active Directly Authentication Library
OD4B: OneDrive 4 Business