// basic signature
Object.mixin(
  target:Object,  // the object to be enriched

  source:Object   // all own properties of this object
                  // will be assigned using same descriptor

):target          // returns the target object modified


// overload with Traits (Function)

Object.mixin(
  target:Object,  // the object to be enriched

  source:Trait    // invoked with target as context

  [, args:Array|Arguments]
                  // optional args property
                  // used at Trait arguments

):target          // returns the target object modified

// using an object

var a = {a: 'b'},
    b = Object.mixin({b: 'b'}, a);

console.log(JSON.stringify(b));
// {"a":"a","b":"b"}


// using a function
function addUniqueIdFunctionality(prefix) {
  var
    privatelyShared = {},
    i = 0
  ;
  if (!prefix) prefix = '.' + (new Date).getTime();
  this.getIdFor = function (key) {
    return privatelyShared[key] || (
      privatelyShared[key] = ++i + prefix + Math.random()
    );
  };
}

function GenericClass(){}

Object.mixin(
  GenericClass.prototype,
  addUniqueIdFunctionality
  // , ['my_prefix']
);

var instance1 = new GenericClass,
    instance2 = new GenericClass;

console.log([
  instance1.getIdFor('a'),
  instance1.getIdFor('b'), // different
  instance2.getIdFor('a')
  // same as instance1.getIdFor('a')
].join('\n'));