Javascript mixin implementation

mixin.js

function mixable() {
  var parents = [];
  return {
    mixin: function(parent) { parents.push(parent); },
    __noSuchMethod__: function(id, args) {
      for each (var parent in parents) {
        if (typeof parent[id] === 'function') {
          return parent[id].apply(this, args);
        }
      }
    }
  };
}

var obj = mixable();

obj.mixin({
  combine: function(a, b){ return a + b; },
});
obj.mixin({
  combine: function(a, b){return a * b}, // order of mixing-in determines precedence, so this will never be called
  subtract: function(a, b) { return a - b }
});

print(obj.combine(1,2));
print(obj.subtract(7,6));