Javascript object class for dealing with ObjectIds as JSON serialized by WCF

Objectid.js

/*
*
* Copyright (c) 2011 Justin Dearing ([email protected])
* Dual licensed under the MIT (http://www.opensource.org/licenses/mit-license.php)
* and GPL (http://www.opensource.org/licenses/gpl-license.php) version 2 licenses.
* This software is not distributed under version 3 or later of the GPL.
*
* Version 1.0.0-RC1
*
*/

/**
* Javascript representation of how WCF serializes a object of type MongoDB.Bson.ObjectId
* and the standard 24 character representation.
*/
var ObjectId = (function () {
    var increment = 0;
    var pid = Math.floor(Math.random() * (32767));
    var machine = Math.floor(Math.random() * (16777216));

    if (typeof (localStorage) != 'undefined') {
        var mongoMachineId = parseInt(localStorage['mongoMachineId']);
        if (mongoMachineId >= 0 && mongoMachineId <= 16777215) {
            machine = Math.floor(localStorage['mongoMachineId']);
        }
        // Just always stick the value in.
        localStorage['mongoMachineId'] = machine;
        document.cookie = 'mongoMachineId=' + machine + ';expires=Tue, 19 Jan 2038 05:00:00 GMT'
    }
    else {
        var cookieList = document.cookie.split('; ');
        for (var i in cookieList) {
            var cookie = cookieList[i].split('=');
            if (cookie[0] == 'mongoMachineId' && cookie[1] >= 0 && cookie[1] <= 16777215) {
                machine = cookie[1];
                break;
            }
        }
        document.cookie = 'mongoMachineId=' + machine + ';expires=Tue, 19 Jan 2038 05:00:00 GMT';

    }

    return function () {
        if (!(this instanceof ObjectId)) {
            return new ObjectId(arguments[0], arguments[1], arguments[2], arguments[3]).toString();
        }

        if (typeof (arguments[0]) == 'object') {
            this.timestamp = arguments[0].timestamp;
            this.machine = arguments[0].machine;
            this.pid = arguments[0].pid;
            this.increment = arguments[0].increment;
        }
        else if (typeof (arguments[0]) == 'string' && arguments[0].length == 24) {
            this.timestamp = Number('0x' + arguments[0].substr(0, 8)),
            this.machine = Number('0x' + arguments[0].substr(8, 6)),
            this.pid = Number('0x' + arguments[0].substr(14, 4)),
            this.increment = Number('0x' + arguments[0].substr(18, 6))
        }
        else if (arguments.length == 4 && arguments[0] != null) {
            this.timestamp = arguments[0];
            this.machine = arguments[1];
            this.pid = arguments[2];
            this.increment = arguments[3];
        }
        else {
            this.timestamp = Math.floor(new Date().valueOf() / 1000);
            this.machine = machine;
            this.pid = pid;
            if (increment > 0xffffff) {
                increment = 0;
            }
            this.increment = increment++;

        }
    };
})();

ObjectId.prototype.getDate = function () {
    return new Date(this.timestamp * 1000);
}

/**
* Turns a WCF representation of a BSON ObjectId into a 24 character string representation.
*/
ObjectId.prototype.toString = function () {
    var timestamp = this.timestamp.toString(16);
    var machine = this.machine.toString(16);
    var pid = this.pid.toString(16);
    var increment = this.increment.toString(16);
    return '00000000'.substr(0, 6 - timestamp.length) + timestamp +
           '000000'.substr(0, 6 - machine.length) + machine +
           '0000'.substr(0, 4 - pid.length) + pid +
           '000000'.substr(0, 6 - increment.length) + increment;
}