Enumerate object's own keys

enumerate.js

// Enumerate over an object's own keys/values, accumulating a value.
// `initial` defines the initial value for the accumulation. Reference is an
// optional additional argument that make a common case -- comparing 2
// objects -- easy and more efficient.
function enumerate(object, next, initial, reference) {
  var accumulated = initial;
  for (var key in object)
    // Test for own keys with `hasOwnProperty` instead of `Object.keys` to
    // avoid garbage creation.
    //
    // @TODO need to test this "optimization".
    if(object.hasOwnProperty(key)) accumulated = next(accumulated, key, object[key], object, reference);
  return accumulated;
}