enum-plus/es/enum-item.js

A drop-in replacement for native enum. Like native enum but much better!

import { Enum } from "./enum";
import { ENUM_ITEM } from "./utils";

/**
 * Enum item class
 *
 * @template V General type of value
 * @template K General type of key
 * @template T Initialize object of enum item
 */
export class EnumItemClass {
  /** Enum item value */
  value;

  /** Enum item label (or called display name) */
  label;

  /** Enum item key */
  key;

  /** Original initialization object */
  raw;
  /**
   * **EN:** A boolean value indicates that this is an enum item instance.
   *
   * **CN:** 布尔值，表示这是一个枚举项实例
   */
  [ENUM_ITEM] = true;
  #localize;
  #localizedProxy = new Proxy(this, {
    get: (target, prop) => {
      const origin = target[prop];
      if (prop === 'label') {
        return target.toString();
      } else if (typeof origin === 'function') {
        return origin.bind(target);
      }
      return origin;
    },
    // Not allowed to edit
    set: (_, prop) => {
      /* istanbul ignore if */
      if (!process.env.JEST_WORKER_ID) {
        console.warn(`Cannot modify property "${String(prop)}" on EnumItem. EnumItem instances are readonly and should not be mutated.`);
      }
      return true;
    },
    defineProperty: (_, prop) => {
      /* istanbul ignore if */
      if (!process.env.JEST_WORKER_ID) {
        console.warn(`Cannot modify property "${String(prop)}" on EnumItem. EnumItem instances are readonly and should not be mutated.`);
      }
      return true;
    },
    deleteProperty: (_, prop) => {
      /* istanbul ignore if */
      if (!process.env.JEST_WORKER_ID) {
        console.warn(`Cannot modify property "${String(prop)}" on EnumItem. EnumItem instances are readonly and should not be mutated.`);
      }
      return true;
    },
    setPrototypeOf: () => {
      /* istanbul ignore if */
      if (!process.env.JEST_WORKER_ID) {
        console.warn('Cannot change prototype of EnumItem. EnumItem instances are immutable.');
      }
      return true;
    }
  });

  /**
   * Instantiate an enum item
   *
   * @param key Enum item key
   * @param value Enum item value
   * @param label Enum item display name
   * @param raw Original initialization object
   * @param options Construction options
   */
  constructor(key, value, label, raw, options) {
    this.key = key;
    this.value = value;
    this.label = label;
    this.raw = raw;
    this.#localize = content => {
      const localize = options?.localize ?? Enum.localize;
      if (typeof localize === 'function') {
        return localize(content);
      }
      return content;
    };

    // @ts-expect-error: because override Object.toPrimitive method to return enum value
    this[Symbol.toPrimitive] = hint => {
      if (hint === 'number') {
        // for cases like Number(value) or +value
        return this.valueOf();
      } else if (hint === 'string') {
        // for cases like String(value), `${value}`
        return this.toString();
      }
      // for cases like '' + value, value == 1
      return this.valueOf();
    };
    // Object.freeze(this);
  }
  readonly() {
    return this.#localizedProxy;
  }
  toString() {
    return this.#localize(this.label) ?? this.label;
  }
  toLocaleString() {
    return this.toString();
  }
  valueOf() {
    return this.value;
  }
}
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