Method resolveBookByKey

js/ReadingSystem.js:111–121

* 根据 key 查找课本 * @param {string} bookKey - 课本标识 key * @returns {Object|null} 匹配的课本对象

(bookKey)

   * @returns {Object|null} 匹配的课本对象
   */
  resolveBookByKey(bookKey) {
    if (!this.state.books.length) return null;

    const exact = this.state.books.find((book) => book?.key === bookKey);
    if (exact?.bookPath) return exact;

    const fallback = this.state.books.find((book) => book?.key === this.config.DEFAULT_BOOK_KEY);
    if (fallback?.bookPath) return fallback;

    return this.state.books.find((book) => book?.bookPath) || null;
  }

  /**
   * 从 URL hash 应用课本