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CustomizeTypeScript SDKextension

Custom validators and expression functions

Add application rules while preserving deterministic validation and expression behavior.

Register custom validators

Subclass Validator for synchronous work or AsyncValidator for a promise. Register the validator as metadata so a JSON definition can name it and the Creator can edit it.

Validator and expression function
import {
  AsyncValidator,
  createDefaultFunctionRegistry,
  globalRegistry,
} from '@kajay/core';

const functions = createDefaultFunctionRegistry();
functions.registerAsync('isserved', async (args) => {
  const postcode = String(args[0] ?? '');
  return checkDeliveryArea(postcode);
});

class ReservedNameValidator extends AsyncValidator {
  override get type(): string { return 'reservednamevalidator'; }
  override async validateAsync({ value }) {
    return (await isReserved(String(value)))
      ? { kind: this.type, text: 'That name is reserved.' }
      : undefined;
  }
}

globalRegistry.addClass({
  name: 'reservednamevalidator',
  parent: 'validator',
  create: () => new ReservedNameValidator(),
});

const { survey } = parseSurvey(definition, { functions });

Use a host-owned function registry

Start from createDefaultFunctionRegistry, register synchronous or asynchronous functions, and pass that registry to parseSurvey. Function names are case-insensitive.

Keep extensions deterministic