id.js

MongoID = {};

MongoID._looksLikeObjectID = function (str) {
  return str.length === 24 && str.match(/^[0-9a-f]*$/);
};

MongoID.ObjectID = function (hexString) {
  //random-based impl of Mongo ObjectID
  var self = this;
  if (hexString) {
    hexString = hexString.toLowerCase();
    if (!MongoID._looksLikeObjectID(hexString)) {
      throw new Error("Invalid hexadecimal string for creating an ObjectID");
    }
    // meant to work with _.isEqual(), which relies on structural equality
    self._str = hexString;
  } else {
    self._str = Random.hexString(24);
  }
};

MongoID.ObjectID.prototype.toString = function () {
  var self = this;
  return "ObjectID(\"" + self._str + "\")";
};

MongoID.ObjectID.prototype.equals = function (other) {
  var self = this;
  return other instanceof MongoID.ObjectID &&
    self.valueOf() === other.valueOf();
};

MongoID.ObjectID.prototype.clone = function () {
  var self = this;
  return new MongoID.ObjectID(self._str);
};

MongoID.ObjectID.prototype.typeName = function() {
  return "oid";
};

MongoID.ObjectID.prototype.getTimestamp = function() {
  var self = this;
  return parseInt(self._str.substr(0, 8), 16);
};

MongoID.ObjectID.prototype.valueOf =
    MongoID.ObjectID.prototype.toJSONValue =
    MongoID.ObjectID.prototype.toHexString =
    function () { return this._str; };

EJSON.addType("oid",  function (str) {
  return new MongoID.ObjectID(str);
});

MongoID.idStringify = function (id) {
  if (id instanceof MongoID.ObjectID) {
    return id.valueOf();
  } else if (typeof id === 'string') {
    if (id === "") {
      return id;
    } else if (id.substr(0, 1) === "-" || // escape previously dashed strings
               id.substr(0, 1) === "~" || // escape escaped numbers, true, false
               MongoID._looksLikeObjectID(id) || // escape object-id-form strings
               id.substr(0, 1) === '{') { // escape object-form strings, for maybe implementing later
      return "-" + id;
    } else {
      return id; // other strings go through unchanged.
    }
  } else if (id === undefined) {
    return '-';
  } else if (typeof id === 'object' && id !== null) {
    throw new Error("Meteor does not currently support objects other than ObjectID as ids");
  } else { // Numbers, true, false, null
    return "~" + JSON.stringify(id);
  }
};


MongoID.idParse = function (id) {
  if (id === "") {
    return id;
  } else if (id === '-') {
    return undefined;
  } else if (id.substr(0, 1) === '-') {
    return id.substr(1);
  } else if (id.substr(0, 1) === '~') {
    return JSON.parse(id.substr(1));
  } else if (MongoID._looksLikeObjectID(id)) {
    return new MongoID.ObjectID(id);
  } else {
    return id;
  }
};