Give all artboards on the page a white _Background layer filling the entire artboard. This fixes the case where you want to export your artboards (perhaps using the excellent "Export All Artboards as PNG" plugin) but don't want transparent PNG background where you intend there to be white.
I figure if you desire a background color other than white, you'll already have it since it's required for display. But you can easily copy and modify the RGB set portion of this script to accomplish other colors.
Just downloading and double-click the .sketchplugin file should work.
If not:
- Open Sketch
- Choose Plugins > Custom Script...
- Gear Menu > Open Plugins Folder
- Drag the .sketchplugin file to that folder that just opened.