js> Object.getPrototypeOf;
function getPrototypeOf() { [native code for Object.getPrototypeOf, arity=1] }

js> // FIXME: not sure if this is correct behaviour, should we be expecting a TypeError here instead?
js> Object.getPrototypeOf() === undefined;
true

js> var nonObjects = [undefined, null, true, 1, 'hello'];
js> nonObjects.every(function(value) { 
  >   try { 
  >     Object.getPrototypeOf(value); 
  >     return false;
  >   } catch (e if e instanceof TypeError) { 
  >     return true; 
  >   } catch (e) {
  >     return false; 
  >   }
  > });
true

js> [(function(){}), [], {}].every(function(obj) { 
  >   return Object.getPrototypeOf(obj) === obj.__proto__; 
  > });
true

js> function UserDefined() {}
js> [Date, UserDefined].every(function(type) {
  >   var instance;
  >   eval('instance = new '+type.name);
  >   return Object.getPrototypeOf(instance) === type.prototype;
  > });
true