code: function def (params, spec, errs) {
    for (var key in params) {
      if (!spec.hasOwnProperty(key)) defError(key, errs)
    }
  }
docs: Ensure that parameter is defined.
  
  @param {Object} params
  Parameters value object.
  
  @param {String} spec
  Parameters definition object.
  
  @param {Array} errs
  Errors list.