test.js

// modifying the calling function's context
// in javascript to emulate operator overloading OR:
// ...
// now you're thinking with portals

var sys = require('sys');
var Toy = function() {
    this.toyList = [];
};

Toy.prototype.valueOf = function() {
    arguments.callee.caller.calledList = arguments.callee.caller.calledList === undefined ? [] : arguments.callee.caller.calledList;
    this.toyList = this.toyList.concat(arguments.callee.caller.calledList).slice();
    arguments.callee.caller.calledList.push(this);
    return this;
};

Toy.prototype.toString = function() {
    return "<Toy of length "+this.toyList.length+">";
};

var testFn = function(name, fn) {
    var t1 = new Toy();
    var t2 = new Toy();
    sys.puts("Result "+name+":\t" + fn(t1, t2));
    sys.puts("\tt1.toyList: "+t1.toyList.length);
    sys.puts("\tt2.toyList: "+t2.toyList.length);
};
var test = {'t1 && t2': function(t1, t2) { return t1 && t2; }
,'t1 || t2':            function(t1, t2) { return t1 || t2; }
,'t1 & t2':             function(t1, t2) { return t1 & t2; }
,'t1 | t2':             function(t1, t2) { return t1 | t2; }
,'t1 / t2':             function(t1, t2) { return t1 / t2; }
,'t1 << t2':            function(t1, t2) { return t1 << t2; }
};

for(var i in test) {
    testFn(i, test[i]);
}