inverted-mixin-1.js

// Mixed.js
define(function() {
  var Mixed = function(a, b) {
    this.a = a;
    this.b = b;
  };
  Mixed.prototype.getA = function() {
    return this.a;
  };
  Mixed.prototype.getB = function() {
    return this.b;
  };
  return Mixed;
});

// ToMix.js
define(function() {
  var ToMix = function(x, y) {
    this.x = x;
    this.y = y;
  };
  ToMix.prototype.getX = function() {
    return this.x;
  };
  ToMix.prototype.getY = function() {
    return this.y;
  };
  return ToMix;
});

inverted-mixin-2.js

define(function() {
  return {
    protos: {
      mixed: {
        module: "Mixed",
        args: [ "A", "B" ],
        //a list of proto references to mix
        mixin: [ "toMix" ]
      },
      toMix: {
        module: "ToMix",
        args: [ "X", "Y" ]
      }
    }
  };
}); 

inverted-mixin-3.js

// Inverted dynamically updates an instance of Mixed 
// which effectively looks like this:
var Mixed = function(a, b) {
  this.a = a;
  this.b = b;

  this.__toMix__; //is an instance of ToMix
};
Mixed.prototype.getA = function() {
  return this.a;
};
Mixed.prototype.getB = function() {
  return this.b;
};
Mixed.prototype.getX = function() {
  return this.__toMix__.getX();
};
Mixed.prototype.getY = function() {
  return this.__toMix__.getY();
};