Guess what. Overloading the JS += operator is possible, if a little contrived and probably unusable!

madhaxx.js

var assert = require("assert");

var store = {};
function resolve(item) {
  return store[item];
}

var FancyObject = function() {
	var arrayProperty = [];
	
	Object.defineProperty(
		this,
		"arrayProperty",
		{
			"set": function(newItem) {
				arrayProperty.push(resolve(newItem));
			},
			"get": function() {
				var prop = arrayProperty.slice(0);
				prop.valueOf = function() {
					return 0;
				}
				return prop;
			}
		}
	);
};

FancyObject.prototype = {};
FancyObject.prototype.valueOf = function() {
	var key = Math.random();
	store[key] = this;
	return key;
}

var assignTo = new FancyObject(),
	assignee = new FancyObject();

assignee.easyIdentifier = 1234567;

console.log(
	"Items in the object we're assigning to? %d",
	assignTo.arrayProperty.length);

assignTo.arrayProperty += assignee;

console.log(
	"Items in the object we're assigning to after increment op: %d",
	assignTo.arrayProperty.length);
	
assert(assignTo.arrayProperty[0].easyIdentifier === 1234567);

cgiffard@crunktown.local overloading
➭  node overloading.js 
Items in the object we're assigning to? 0
Items in the object we're assigning to after increment op: 1