code: function val (params, spec, errs) {
    for (var key in params) {
      if (key in spec && isFunction(spec[key].val) && !spec[key].val(params[key])) valError(key, errs)
    }
  }
docs: Ensure that validation predicates pass.
  
  @param {Object} params
  Parameters value object.
  
  @param {String} spec
  Parameters definition object.
  
  @param {Array} errs
  Errors list.