Delete ItemLevel-Permission

Hi,

I have been using the javascript-object-model quite extensively in the last few weeks. Sometimes documentation can be difficult to find, as for my newest problem:

I am trying to update listItem-permissions on a sharepoint list-item and therefore I have to delete all existing permissions beforehand. Setting permissions works but I wasnt able to find a way to delete them using REST or JSOM (thus using javascript).

So if anyone knows how to do that in REST or JSOM please replay...

Thank you for your time!