SharePoint React WebParts
Refer to this blog post for details on the available webparts to inherit from. The blog post gives an overview of the code for the "Document View WebPart" example.
Batch Demo WebPart
An example of the executing batch operations. Refer to this link for Microsoft's documentation for performing batch operations using the SharePoint Online REST API.
Document View WebPart
Simple example of using the WebPartSearch classes to display documents. The search webpart class allows the user to select the searchable fields, currently limited to:
A mapper will be generated from the field values, and used as a tag picker for filtering the documents. Clicking on an office document will display it in the office app.
Simple example of using the SP People Picker component and the email class of the gd-sprest library.
Hello World WebPart
Probably the first one you should look at. It's a simple example of using the webpart component, and the OnRenderDisplay and OnRenderEdit events. The page will render the webpart id in display mode, and a message indicating it's an edit mode when the page is being edited.
An example of extending the WebPart Search class to display a list view and item form. The "ItemForm" component will be used to render the item form panel.
An example of using the WebPart Tabs class to generate a tab for each associated webpart in the same zone.