个人中心
gpt4 book ai didi

javascript - 尝试打开具有更高版本号的数据库时触发 onblocked

转载 作者：行者123 更新时间：2023-11-30 19:39:35 25 4
gpt4 key购买 nike

我正在创建 indexedDB 数据库 products_db。

  • onload 添加 objectStore products_os 到数据库。
  • 从服务器获取数据并将数据添加到 products_os。
  • 在 UI 中显示数据。
  • onclick 的 add 按钮，尝试打开具有更高版本号的数据库并创建一个新的 objectStore cart_os。 这是它没有按预期工作的地方。

当前行为:

  • 当我以隐身模式打开 chrome 浏览器并在选项卡中加载我的 index.html 文件时，UI 中会显示一个表格行，但在 Application 选项卡中Developer Tools indexedDB 中没有 product_db 数据库。
  • 点击添加按钮时，onblocked 事件的警报如在function addCartData(e) { 弹出。 (此站点打开时没有其他选项卡!)。关闭弹出窗口后，现在点击相同的添加按钮不会执行任何操作。
  • 现在，如果我使用 cmd + shift + r 刷新页面，一个新行将附加到表格中。现在共有两行​​。每次刷新时，都会附加一个新行。上一点对于 UI 中的所有添加按钮都是正确的，单击任何一个都会触发警报，然后所有按钮都变得无用。(没有弹出 onclick)。
  • 如果我清除存储然后执行 cmd + shift + r，我再次在 UI 中只得到一行。

预期行为:

    Developer tools 的 Application 选项卡中的
  • indexedDB 不应为空。相反，它应该填充 db 和 objectStore。
  • 刷新时，在不清除存储的情况下，应该只有一行每次都显示。
    • 添加按钮的
  • onclick，应使用新版本号打开数据库，并向其中添加 objectStore cart_os。以便稍后我可以使用 cart_os 进行 read/write 交易。

index.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Product Table</title>
    <link href="styles.css" rel="stylesheet">
    <script src="script.js" defer></script>
  </head>
  <body>
    <table id='idb-table' style="width=100%" />
  </body>
</html>

脚本.js

// Create an instance of a db object for us to store the open database in
let db;

window.onload = function() {
  // Open our database; it is created if it doesn't already exist
  let request = window.indexedDB.open('products_db', 1);

  // onerror handler signifies that the database didn't open successfully
  request.onerror = function() {
    console.log('Database failed to open');
  }

  // onsuccess handler signifies that the database opened successfully
  request.onsuccess = function() {
    console.log('Database opened successfully');

    // Store the opened database object in the db variable. This is used a lot below
    db = request.result;

    // Run the fetchProducts() function to fetch data from external API 
    fetchProducts();
  }

  // Setup the database tables if this has not already been done
  request.onupgradeneeded = function(e) {
    // Grab a reference to the opened database
    let db = e.target.result;

    // Create an objectStore to store our products in (basically like a single table)
    // including a auto-incrementing key
    let objectStore = db.createObjectStore('products_os', {keyPath: 'id', autoIncrement: true});

    // Define what data items the objectStore will contain
    objectStore.createIndex('title', 'title', {unique: false});
    objectStore.createIndex('price', 'price', {unique: false});
    objectStore.createIndex('inStock', 'inStock', {unique: false});

  }

  function fetchProducts() {
    let product1 = fetch('http://localhost:3001/location/pathname') // see product.json file
      .then(function(response) {
        return response.json();
      })
      .then(function(response) {
        addData(response);
      })
  }

  function addData(value) {
    // open a read/write db transaction, ready for adding the data
    let transaction = db.transaction(['products_os'], 'readwrite');

    // call an object store that's already been added to the database
    let objectStore = transaction.objectStore('products_os');

    let newItem = {
      title: value.title,
      price: value.sellingPrice,
      inStock: value.inStock,
    };

    // Make a request to add our newItem object to the object store
    var request = objectStore.add(newItem);

    transaction.oncomplete = function() {
      console.log('Transaction completed: database modification finished.');

      // update the display of data to show the newly added item, by running displayData() again.
      displayData();
    }

    transaction.onerror = function() {
      console.log('Transaction not opened due to error');
    };
  }

  function displayData() {
    // Open our object store and then get a cursor - which iterates through all the
    // different data items in the store
    let objectStore = db.transaction('products_os').objectStore('products_os');

    objectStore.openCursor().onsuccess = function(e) {
      // Get a reference to the cursor
      let cursor = e.target.result;

      // Get a reference to table
      let table = document.querySelector('#idb-table');

      // If there is still another data item to iterate through, keep running this code
      if(cursor) {
        // Insert into table,
        // structure the HTML fragment, and append it inside the table
        let tableRow = document.createElement('tr');
        for (let val in cursor.value) {
          if (Object.prototype.hasOwnProperty.call(cursor.value, val)) {
            if (val !== 'id') {
              let td = document.createElement('td');
              tableRow.appendChild(td);
              td.textContent = cursor.value[val];
            }
          }
        }
        let td = document.createElement('td');
        td.setAttribute('align', 'center');
        let addButton = document.createElement('button');
        td.appendChild(addButton);
        addButton.textContent = 'Add';
        addButton.addEventListener('click', function(e) {
          addCartData(e);
        })
        tableRow.appendChild(td);
        table.appendChild(tableRow);

        // Iterate to the next item in the cursor
        cursor.continue();
      }
    }
  }

  function addCartData(e) {
    // Open the db with higher version number
    let req = window.indexedDB.open('products_db', 2);

    req.onerror = function() {
      console.log('Database failed to open');
    }

    req.onsuccess = function() {
      console.log('Database opened successfully');

      // Store the opened database object in the db variable. This is used a lot below
      db = req.result;
    }

    req.onblocked = function(event) {
      // If some other tab is loaded with the database, then it needs to be closed
      // before we can proceed.
      alert("Please close all other tabs with this site open!");
    };

    req.onupgradeneeded = function(e){
      // Grab a reference to the opened database
      let db = e.target.result;

      // Create a cart objectStore to store our information added to the cart
      let cartStore = db.createObjectStore('cart_os', {keyPath: 'id', autoIncrement: true});

      // Define what data items the cart objectStore will contain
      cartStore.createIndex('title', 'title', {unique: false});
      cartStore.createIndex('price', 'price', {unique: false});
    }
  }

样式.css

table {
  font-family: arial, sans-serif;
  border-collapse: collapse;
  width: 100%;
} 

td, th {
  border: 1px solid #dddddd;
  text-align: left;
  padding: 8px;
}   

tr:nth-child(even) {
  background-color: #dddddd;
} 

tr:last-child {
  text-align: center!important;
}

产品.json

{
   "title": "Newhide Designer",
   "productDescription": "",
   "sellingPrice": 119,
   "inStock": true,
}

编辑

objectStore products_os was never added to db

我收到错误 Uncaught (in promise) DOMException: Failed to execute 'transaction on 'IDBDatabase': One of the specified object stores was not found. at line 207 如图所示。

onupgradeneeded_version1:

function onupgradeneeded_version1(e) {
  // Grab a reference to the opened database
  let db = e.target.result;

  // Create an objectStore to store our products in (basically like a single table)
  // including a auto-incrementing key
  let objectStore = db.createObjectStore('products_os', {keyPath: 'id', autoIncrement: true});

  // Define what data items the objectStore will contain
  objectStore.createIndex('title', 'title', {unique: false});
  objectStore.createIndex('price', 'price', {unique: false});
  objectStore.createIndex('inStock', 'inStock', {unique: false});
}

最佳答案

嗯，关于如何改进这段代码，我有很多建议，但直截了本地说，我认为问题源于这样一个事实，即您最初打开一个数据库连接，并保持它打开(无限期地) )，然后在您的单击处理程序中，打开具有更高版本号的第二个数据库版本，如果单击该版本，则在初始数据库连接仍处于打开状态时发生。

我建议将 indexedDB.open => db 逻辑封装在一个 promise 中。这将使代码更易于阅读和编写。然后我建议改变您使用该 promise 的方式。

这是我的想法:

function open(name, version, onupgradeneeded) {
  return new Promise(function executor(resolve, reject) {
    const request = indexeDB.open(name, version);
    request.onsuccess = function(event) { resolve(request.result); };
    request.onerror = function(event) { reject(request.result); };
    request.onblocked = function(event) { console.debug('blocked indefinitely'); };
    request.onupgradeneeded = onupgradeneeded;
  });
}

async function fetch_product() {
  const response = await fetch('http://localhost:3001/location/pathname');
  const data = await response.json();
  return data;
}

function add_product(db, data) {
  return new Promise(function(resolve, reject) {
    const transaction = db.transaction(..., 'readwrite');
    transaction.oncomplete = resolve;
    transaction.onerror = reject;
    const store = transaction.objectStore(...);
    store.put(data);
  });
}

function get_products(db) {
  return new Promise(function(resolve, reject) {
    const transaction = db.transaction(...);
    const store = transaction.objectStore(...);
    const request = store.getAll();
    request.onsuccess = function(event) {
      const products_array = request.result;
      resolve(products_array);
    };
    request.onerror = function(event) {
      reject(request.error);
    };
  });
}

function render_product(product) {
  const table = document.getElementById('table-id');

  // create rows and all that.
  // and append
  button.onclick = handle_click;
}

async function handle_click(event) {

  // Based on what was clicked, find and build the product data object
  // event.target is the button
  const row = event.target.closest('tr');
  const name = row.querySelector('td.namecolumn').textContent;
  // etc
  const product = {
    name: name
  };

  const db = await open(name, version2, onupgradeneeded_for_version2);
  await add_product(db, product);
  db.close();
}

async function onload() {
  const product = await fetch_product();
  const db = await open(name, version, onupgradeneeded_version1);
  await add_product(db, product);

  const products = await get_products(db);

  // we are done with the db now
  db.close();

  // print out product data
  for(const product of products) {
    render_product(product);
  }  
}

关于javascript - 尝试打开具有更高版本号的数据库时触发 onblocked，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/55550726/

25 4 0
文章推荐： c - 将列表写入文本文件
文章推荐： javascript - 如何从 node.js 检索数据到 Ajax？
文章推荐： javascript - 我定义了一些变量并使用它们来检索有效的纬度和经度，但是在我将变量传递给另一个函数后不起作用
文章推荐： c - 为什么这段 C 代码会崩溃
行者123
个人简介

我是一名优秀的程序员,十分优秀！

滴滴打车优惠券免费领取
滴滴打车优惠券
全站热门文章
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com