function checkParams(params){   //params is an object with key/value pairs

  var name, value,
      errCode, errMsg;
  f:for (name in params){
    s:switch (name) {
      case 'param1':
        if (...params[name] valid...) {
          break s;
        }
        errCode = 1;
        errMsg = 'Whoops, error in param ' + name;
        break f;
      case ...etc...
        ...many more cases...
    }
  }
  if (errCode) {
    throw {
      code: errCode,
      msg: errMsg
    };
  }
}