var $             = require('./$')
  , HAS_INSTANCE  = require('./$.wks')('hasInstance')
  , FunctionProto = Function.prototype;
// 19.2.3.6 Function.prototype[@@hasInstance](V)
if(!(HAS_INSTANCE in FunctionProto))$.setDesc(FunctionProto, HAS_INSTANCE, {value: function(O){
  if(!$.isFunction(this) || !$.isObject(O))return false;
  if(!$.isObject(this.prototype))return O instanceof this;
  // for environment w/o native `@@hasInstance` logic enough `instanceof`, but add this:
  while(O = $.getProto(O))if(this.prototype === O)return true;
  return false;
}});