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GoodStaffAdvent Calendar 2017

Day 6

indexedDB の基本をまとめてみた

Last updated at Posted at 2017-12-06

indexedDBとは

値とオブジェクトをローカルデータベースに保持するウェブブラウザの標準インターフェース


DBに接続

open

var request = window.indexedDB.open('MyTestDatabase')

第2引数にバージョンを指定することができる


エラーハンドラを設定する

var db;

// DB に接続
var request = indexedDB.open("MyDatabase");

// 接続失敗
request.onerror = function(event) {
 alert("接続に失敗しました");
};

// 接続成功
request.onsuccess = function() {
  db = event.target.result;
};

スキーマを作成

openするとonupgradeneededイベントが呼び出されます

var db
var request = indexedDB.open('MyDatabase', 1)
var index
var store
request.onupgradeneeded = function () {
    db = request.result

    // MyObjectStore を作成 key は id
    store = db.createObjectStore('MyObjectStore', {keyPath: 'id'})

    // インデックスを作成 key は name.last, name.first 
    index = store.createIndex('NameIndex', ['name.last', 'name.first'])
}

データの書き込み

db = request.result

//  readwrite : 読み書きを開始
var tx = db.transaction('MyObjectStore', 'readwrite')
store = tx.objectStore('MyObjectStore')
index = store.index('NameIndex')

// データの追加
store.put({id: 12345, name: {first: 'John', last: 'Doe'}, age: 42})
store.put({id: 67890, name: {first: 'Bob', last: 'Smith'}, age: 35})

データの呼び出し

// store からデータ取得 key は id
var getJohn = store.get(12345)
// => {id: 12345, name: {first: 'John', last: 'Doe'}, age: 42}

// index からデータ取得 key は [name.last, name.first]
var getBob = index.get(['Smith', 'Bob'])
// => {id: 67890, name: {first: 'Bob', last: 'Smith'}, age: 35}

getJohn.onsuccess = function () {
  console.log(getJohn.result.name.first)  // => "John"
}

getBob.onsuccess = function () {
  console.log(getBob.result.name.first)   // => "Bob"
}

// 読み書き終了
tx.oncomplete = function () {
  db.close()
}

参考

IndexedDB を使用する - Web API インターフェイス | MDN

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