help class to validate objects and throw if problems

I have a C# class that I use all the time for quick and rough data validation and I missed it in javascript.  I created the start of the class with just a few methods but thought I would share here if others are interested.

 /*   * Data validation helper class.   * Various static methods to validate object values.   */  function Guard(){}  Guard.NotNull = function Guard_NotNull(obj, msg)  {      Guard.CheckMessage(msg);            if(obj == null)      {          throw nlapiCreateError('NULL_REFERENCE', msg);      }  }  Guard.SizeEquals = function Guard_SizeEquals(actual, expected, msg)  {      Guard.CheckMessage(msg);      Guard.NotNull(actual, 'actual cannot be null');      Guard.NotNull(expected, 'expected cannot be null');            if(actual != expected)      {          throw nlapiCreateError('INVALID_SIZE', msg + 'nExpected Size: '              + expected + 'nActual Size: ' + actual);      }  }  Guard.NotNullOrEmpty = function Guard_NotNullOrEmpty(obj, msg)  {      Guard.CheckMessage(msg);            if(obj == null || (obj != null && obj.length && obj.length < 1)          || obj == '')      {          throw nlapiCreateError('NULL_OR_EMPTY_VALUE',