dreamstate/esm/development/utils/createComputed.js

Store management library based on react context and observers

import { DreamstateError } from '../core/error/DreamstateError.js';
import { ComputedValue } from '../core/storing/ComputedValue.js';
import { EDreamstateErrorCode } from '../types/error.js';
import { isFunction, isUndefined } from './typechecking.js';

/**
 * Creates a computed value that will be re-calculated after each context update.
 * The computed value is recalculated only when its dependencies, as determined by the memo function,
 * are updated.
 *
 * @template T The type of the computed value.
 * @template C The type of the context the computed value depends on.
 * @param {Function} selector A generic selector function that returns computed values on update.
 * @param {Function} memo An optional memo checker function that returns an array of dependencies,
 *   indicating whether the computed value should be updated.
 * @returns {TComputed<T, C>} A computed value object that will be updated based on context changes.
 */
function createComputed(selector, memo) {
  if (isFunction(selector) && (isUndefined(memo) || isFunction(memo))) {
    // Cast computed to T & TComputed since it works like state object later.
    return new ComputedValue(selector, memo);
  } else {
    throw new DreamstateError(EDreamstateErrorCode.INCORRECT_PARAMETER, "Computed value should be initialized with functional selector and optional memo function.");
  }
}

export { createComputed };