indexedDB - 在类构造函数中使用promise - 无法读取属性＆＃39; transaction＆＃39;未定义的

Question

我正在尝试编写一个返回使用indexedDB的方法的类（我需要一个可重用的API来与我的其他Web应用程序共享）。

这是我的构造函数到目前为止的样子：

Dim i as Long
For i = 1 to 10
    Cells(i,"C").Formula = Cells(i,"A").Value + Cells(i,"B").Value
Next i

然后我在另一个文件（我的商店）中导入客户端：

const IndexDbParams = {
  // Update this when changing the db schema
  dbVersion: 1,
  // Database, object store names
  databaseName: "CropViewData",
  fieldsObjectStoreName: "fieldsData",
  filedObjectStoreKeyName: "key",
  zoneMapObjectStoreName: "zoneMapData"
};

class IndexDbClient {
  constructor() {
    this.initializeDB().then(db => (this.db = db));
  }

  async initializeDB() {
    return new Promise((resolve, reject) => {
      const {
        dbVersion,
        databaseName,
        fieldsObjectStoreName,
        filedObjectStoreKeyName
      } = IndexDbParams;
      // Open a connection to indexDB
      const DbOpenRequest = window.indexedDB.open(databaseName, dbVersion);
      DbOpenRequest.onsuccess = e => {
        const db = DbOpenRequest.result;
        // Create data stores if none exist
        if (db.objectStoreNames.length < 1) {
          if (db.objectStoreNames.indexOf(fieldsObjectStoreName) < 0) {
            db.createObjectStore(fieldsObjectStoreName, {
              keyPath: filedObjectStoreKeyName
            });
          }
        }
        // return db object, will come hore from onupgradeneeded as well
        resolve(db);
      };
      // If we need to upgrade db version
      DbOpenRequest.onupgradeneeded = e => {
        const db = event.target.result;
        const objectStore = db.createObjectStore(fieldsObjectStoreName, {
          keyPath: filedObjectStoreKeyName
        });
      };
    });
  }

  getFieldData(compareFunction, queryParams) {
    return new Promise((resolve, reject) => {
      const { fieldsObjectStoreName } = IndexDbParams;
      const transaction = this.db.transaction(
        fieldsObjectStoreName,
        "readonly"
      );
      // If db transaction fails, reject
      transaction.onerror = e => {
        reject(transaction.error);
      };
      const objectStore = transaction.objectStore(fieldsObjectStoreName);
      const cursor = objectStore.openCursor();
      // const to store query results
      const results = [];
      cursor.onsuccess = event => {
        const result = cursor.result;
        // If we have a entry
        if (result) {
          // evaluate function here
          if (compareFunction(queryParams, result)) {
            // Add the entry to the results array
            results.push(result.value);
          }
          // If we have no more entries
        } else {
          // Return all results
          resolve(results);
        }
      };
      cursor.onerror = event => {
        reject(cursor.error);
      };
    });
  }

  getFieldById(fieldId) {
    return new Promise((resolve, reject) => {
      this.getFieldData(this.byId, { id: fieldId })
        .then(data => {
          resolve(data);
        })
        .catch(e => {
          reject(e);
        });
    });
  }

  byId({ id }, field) {
    return field.id === id;
  }

}

export default IndexDbClient;

我收到错误：

  

未捕获（承诺）TypeError：无法读取属性＆＃39;事务＆＃39;的   未定义

如果我从控制台运行相同的功能，则错误不存在。我假设这是由于构造函数没有将db对象分配给IndexDbClient？有没有办法让我解决这个问题 - 我看到它的方式我必须等待import IndexDbClient from "../facades/IndexDbClient"; const db = new IndexDbClient(); db.getFieldById("fe276ead-def3-47a6-aefd-020e844774af").then(res => { console.log(res); }); 方法中的.onsucess事件才能确保indexedDB连接是打开的？