how to get an array out of a javascript proxy

I was wondering how to get an array out of a proxy's target value in JavaScript. I have something like this :

Proxy :
  [[target]] : Array // the array I need to extract
  [[handler]] : Object 
  [[IsRevoked]] : false

If all you have is a reference to the proxy, there is no way (by default) for you to get the proxy's target. A specific proxy could provide a way (via one of its trap handlers, probably), but there is none by default.