indexdb增删改查示例

IndexedDB 是一个低级 API，用于在用户的浏览器中存储大量结构化数据。下面是增删改查（CRUD）操作的基本示例：

1. 打开数据库并创建对象存储

let db;
const request = indexedDB.open('myDatabase', 1);

request.onerror = function(event) {
  console.error('Database error:', event.target.errorCode);
};

request.onsuccess = function(event) {
  db = event.target.result;
  console.log('Database opened successfully');
};

request.onupgradeneeded = function(event) {
  db = event.target.result;
  const objectStore = db.createObjectStore('myObjectStore', { keyPath: 'id' });
  objectStore.createIndex('name', 'name', { unique: false });
  objectStore.createIndex('email', 'email', { unique: true });
};

2. 添加数据（Create）

function addData(data) {
  const transaction = db.transaction(['myObjectStore'], 'readwrite');
  const objectStore = transaction.objectStore('myObjectStore');
  const request = objectStore.add(data);

  request.onsuccess = function(event) {
    console.log('Data added successfully');
  };

  request.onerror = function(event) {
    console.error('Unable to add data:', event.target.errorCode);
  };
}

// 示例数据
const newData = { id: 1, name: 'John Doe', email: 'john@example.com' };
addData(newData);

3. 读取数据（Read）

function readData(id) {
  const transaction = db.transaction(['myObjectStore'], 'readonly');
  const objectStore = transaction.objectStore('myObjectStore');
  const request = objectStore.get(id);

  request.onerror = function(event) {
    console.error('Unable to retrieve data from database:', event.target.errorCode);
  };

  request.onsuccess = function(event) {
    if (request.result) {
      console.log('Data retrieved:', request.result);
    } else {
      console.log('No data found with ID:', id);
    }
  };
}

// 查询 ID 为 1 的数据
readData(1);

4. 更新数据（Update）

function updateData(data) {
  const transaction = db.transaction(['myObjectStore'], 'readwrite');
  const objectStore = transaction.objectStore('myObjectStore');
  const request = objectStore.put(data);

  request.onsuccess = function(event) {
    console.log('Data updated successfully');
  };

  request.onerror = function(event) {
    console.error('Unable to update data:', event.target.errorCode);
  };
}

// 更新 ID 为 1 的数据
const updatedData = { id: 1, name: 'Jane Doe', email: 'jane@example.com' };
updateData(updatedData);

5. 删除数据（Delete）

function deleteData(id) {
  const transaction = db.transaction(['myObjectStore'], 'readwrite');
  const objectStore = transaction.objectStore('myObjectStore');
  const request = objectStore.delete(id);

  request.onsuccess = function(event) {
    console.log('Data deleted successfully');
  };

  request.onerror = function(event) {
    console.error('Unable to delete data:', event.target.errorCode);
  };
}

// 删除 ID 为 1 的数据
deleteData(1);

这些示例展示了如何在 IndexedDB 中进行基本的增删改查操作。请确保在实际应用中根据需要调整对象存储和索引的定义。