onValidation.js

import("Util_lib");
import("system.result");
import("system.vars");
import("Attribute_lib");

var attributeType = AttributeTypes.get(vars.get("$field.ATTRIBUTE_TYPE"));
if (attributeType && !attributeType.useLookup)
{
    var validationResult = attributeType.validateValue(vars.get("$local.value"), Utils.parseJSON(vars.get("$field.VALIDATIONPARAMETERS")));
    if (validationResult && validationResult !== true)
        result.string(validationResult);
}