introduce

IndexedDB is a low-level API for storing large amounts of structured data on the client side. At present, all browsers have been supported, and the compatibility is very good.

features

IndexedDB is a JavaScript-based object-oriented database, IndexedDB allows you to store and retrieve objects indexed with keys ;
Any object supported by the structured cloning algorithm can be stored;
Use indexes to enable high-performance searching of data;
Most of the IndexedDB API is asynchronous. The data will not be provided through the return value, but a callback function will be passed to get the return value;
IndexedDB obeys the same-origin policy . When you operate and store data under a certain domain name, you cannot operate data under other domain names;
Can store files/binary large objects (blobs);
Available in Web Workers;
IndexedDB is a transactional database system.

use

To gain access to the database, call the open() method on the indexedDB (en-US) property of the window object. This method returns an IDBRequest object; asynchronous operations communicate with the calling program by firing events on the IDBRequest object.

The specific use can see the following code:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0">
  <title>Title</title>
  <link href="./favicon.png">
</head>
<body>
</body>
<script>
  let dbName = 'helloIndexDB', version = 1, storeName = 'helloStore'
 
  let indexedDB = window.indexedDB
  let db
  const request = indexedDB.open(dbName, version)
  request.onsuccess = function(event) {
    db = event.target.result // 数据库对象
    console.log('数据库打开成功')
  }
 
  request.onerror = function(event) {
    console.log('数据库打开报错')
  }
 
  request.onupgradeneeded = function(event) {
    // 数据库创建或升级的时候会触发
    console.log('onupgradeneeded')
    db = event.target.result // 数据库对象
    let objectStore
    if (!db.objectStoreNames.contains(storeName)) {
      objectStore = db.createObjectStore(storeName, { keyPath: 'id' }) // 创建表
      // objectStore.createIndex('name', 'name', { unique: true }) // 创建索引 可以让你搜索任意字段
    }
  }
 
 
  // 添加数据
  function addData(db, storeName, data) {
    let request = db.transaction([storeName], 'readwrite') // 事务对象 指定表格名称和操作模式（"只读"或"读写"）
      .objectStore(storeName) // 仓库对象
      .add(data)
 
    request.onsuccess = function(event) {
      console.log('数据写入成功')
    }
 
    request.onerror = function(event) {
      console.log('数据写入失败')
      throw new Error(event.target.error)
    }
  }
 
  // 根据id获取数据
  function getDataByKey(db, storeName, key) {
      let transaction = db.transaction([storeName]) // 事务
      let objectStore = transaction.objectStore(storeName) // 仓库对象
      let request = objectStore.get(key)
 
      request.onerror = function(event) {
        console.log('事务失败')
      }
 
      request.onsuccess = function(event) {
        console.log('主键查询结果: ', request.result)
      }
  }
 
  // 根据id修改数据
  function updateDB(db, storeName, data) {
    let request = db.transaction([storeName], 'readwrite') // 事务对象
      .objectStore(storeName) // 仓库对象
      .put(data)
 
    request.onsuccess = function() {
      console.log('数据更新成功')
    }
 
    request.onerror = function() {
      console.log('数据更新失败')
    }
  }
 
  // 根据id删除数据
  function deleteDB(db, storeName, id) {
    let request = db.transaction([storeName], 'readwrite').objectStore(storeName).delete(id)
 
    request.onsuccess = function() {
      console.log('数据删除成功')
    }
 
    request.onerror = function() {
      console.log('数据删除失败')
    }
  }
 
  // 由于打开indexDB是异步的加个定时器避免 db对象还没获取到值导致 报错
  setTimeout(() => {
    addData(db, storeName, {
      id: new Date().getTime(), // 必须且值唯一
      name: '张三',
      age: 18,
      desc: 'helloWord'
    })
 
    getDataByKey(db, storeName, 1638160036008)
 
    updateDB(db, storeName, {id: 1638164880484, desc: '修改的内容'})
 
    deleteDB(db, storeName, 1638164870439)
  }, 1000)
 
</script>
</html>

quick access

At present, there are many packaged third-party libraries, such as the following, you can choose according to your needs:

localForage : A simple polyfill that provides simple value syntax for client-side data storage. It uses IndexedDB behind the scenes and falls back to WebSQL or localStorage in browsers that don't support IndexedDB.
Dexie.js : A wrapper for IndexedDB, with a simple syntax for faster code development.
ZangoDB : An IndexedDB-like interface to MongoDB that supports most of MongoDB's familiar filtering, projection, sorting, updating, and aggregation functions.
JsStore : An IndexedDB wrapper with SQL syntax.

Front-end local storage database IndexedDB storage files

introduce

features

use

quick access

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