A plural ES5 + ES6 friendly version of Object.getOwnPropertyDescriptor

Object.getOwnPropertyDescriptors.js

'getOwnPropertyDescriptors' in Object || (
  Object.getOwnPropertyDescriptors = function (Object) {
    var
      gOPD    = Object.getOwnPropertyDescriptor,
      gOPN    = Object.getOwnPropertyNames,
      gOPS    = Object.getOwnPropertySymbols,
      gNS     = gOPS ? function (object) {
                         return gOPN(object).concat(gOPS(object));
                       } :
                       gOPN,
      descriptors
    ;
    function copyFrom(key) {
      descriptors[key] = gOPD(this, key);
    }
    return function getOwnPropertyDescriptors(object) {
      var result = descriptors = {};
      gNS(object).forEach(copyFrom, object);
      descriptors = null;
      return result;
    };
  }(Object)
);

An alternate polyfillable ES6 version that relies on Reflect.ownKeys, Array#reduce, and Object.getOwnPropertyDescriptor:

function getOwnPropertyDescriptors(obj) {
  return Reflect.ownKeys(obj).reduce(function (acc, key) {
    acc[key] = Object.getOwnPropertyDescriptor(obj, key);
    return acc;
  }, {});
}

(just posting this comment here so I don't forget it later ;-) )

A possible Object.copy that works like Object.assign but includes getters, setters, and non enumerable properties too.

Object.copy = (function (O) {
  var
    dP    = O.defineProperty,
    gOPD  = O.getOwnPropertyDescriptor,
    gOPN  = O.getOwnPropertyNames,
    gOPS  = O.getOwnPropertySymbols,
    set   = function (target, source) {
      for (var
        key,
        keys = gOPN(source).concat(gOPS(source)),
        i = 0,
        l = keys.length; i < l; i++
      ) {
        key = keys[i];
        dP(target, key, gOPD(source, key));
      }
    }
  ;
  return function copy(target) {
    for (var i = 1, l = arguments.length; i < l; i++) {
      set(target, arguments[i]);
    }
    return target;
  };
}(Object));