OL3 (v3.20.0 ), draw holes on polygons. (javascript)

As ol3 have not yet implemented the "draw hole" vector functionality, I did a bit of work to achive it. So, in the meantime, my approach may help you. After the last update it works using 3.20.0 latest openlayers3 version. Propably it works with older versions as well but havent tested.

Also not that I use jsts library in order to verify whether drawn hole vertex is inside a polygon. 

Here is a demo  here(jsfiddle) (updated on 16/12/2016)

preview




It only works for simple (not multi) polygons. But you may add as many holes you like in a single polygon. It also lucks the visual hole effect during drawing (fixed with the new update).
Also prevents the draw hole ouside the selected polygon. 
I ll try to work with these and if I get something better I ll let you know.

Openlayers 3 new version 3.8

open layers version 3.8 launched.
release notes may be found here --> release notes
2 patches have been released. So you better download the patched version which may be downloaded from here -->v3.8.2.zip.
Still wait, for the vector api, the donut polygon support (intermediate solution for donut polygon may be found here -->draw hole fiddle ) as well as the undo/redo interaction. Hope to get these on next version.
There is also a new version for the ol3-cesium based on this new open layers version.
ol3-cesium v1.7 may be downloaded from here -->get it