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IndexedDB API 的 IDBOpenDBRequest 接口提供了访问打开或删除数据库的请求的结果(通过调用 IDBFactory.open and IDBFactory.deleteDatabase),途径就是使用特殊的事件处理器属性。

Note: 此特性在 Web Worker 中可用。

Properties

Also inherits methods from its parents IDBRequest and EventTarget.

Events

IDBOpenDBRequest.onblocked
The event handler for the blocked event. This event is triggered when the upgradeneeded event should be triggered because of a version change but the database is still in use (i.e. not closed) somewhere, even after the versionchange event was sent.
IDBOpenDBRequest.onupgradeneeded
upgradeneeded 事件的事件处理器,会在当一个数据库的版本比已经存在的版本还高的时候触发。

Methods

No methods, but inherits methods from its parents IDBRequest and EventTarget.

Example

In the following example you can see the onupgradeneeded handler being used to update the database structure if a database with a higher version number is loaded. For a full working example, see our To-do Notifications app (view example live.)

var db;

// Let us open our database
var DBOpenRequest = window.indexedDB.open("toDoList", 4);

// these event handlers act on the database being opened.
DBOpenRequest.onerror = function(event) {
  note.innerHTML += '<li>Error loading database.</li>';
};

DBOpenRequest.onsuccess = function(event) {
  note.innerHTML += '<li>Database initialised.</li>';
 
  // store the result of opening the database in the db
  // variable. This is used a lot below
  db = DBOpenRequest.result;
 
  // Run the displayData() function to populate the task
  // listwith all the to-do list data already in the IDB
  displayData();
};

// This event handles the event whereby a new version of
// the database needs to be created Either one has not
// been created before, or a new version number has been
// submitted via the window.indexedDB.open line above
// it is only implemented in recent browsers
DBOpenRequest.onupgradeneeded = function(event) {
  var db = this.result;
 
  db.onerror = function(event) {
    note.innerHTML += '<li>Error loading database.</li>';
  };

  // Create an objectStore for this database   
  var objectStore = db.createObjectStore("toDoList", { keyPath: "taskTitle" });

  // define what data items the objectStore will contain
    
  objectStore.createIndex("hours", "hours", { unique: false });
  objectStore.createIndex("minutes", "minutes", { unique: false });
  objectStore.createIndex("day", "day", { unique: false });
  objectStore.createIndex("month", "month", { unique: false });
  objectStore.createIndex("year", "year", { unique: false });
  objectStore.createIndex("notified", "notified", { unique: false });
};

Specifications

Specification Status Comment
Indexed Database API
IDBOpenDBRequest
Recommendation Initial definition
Indexed Database API 2.0
IDBOpenDBRequest
Recommendation  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support

24

23 — 57 webkit

Yes

16

10 — 16 moz

101157
Available in workers Yes ?37 ? Yes ?
onblocked

24

23 — 57 webkit

12

16

10 — 16 moz

101157
onupgradeneeded

24

23 — 57 webkit

12

16

10 — 16 moz

101157
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support

24

23 — 57 webkit

24

23 — 57 webkit

Yes22228

Yes

Yes — 7.0 webkit

Available in workers Yes Yes Yes37 Yes ? Yes
onblocked

24

23 — 57 webkit

24

23 — 57 webkit

Yes22228

Yes

Yes — 7.0 webkit

onupgradeneeded

24

23 — 57 webkit

24

23 — 57 webkit

Yes22228

Yes

Yes — 7.0 webkit

1. partial

See also

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