IDBCursor.continuePrimaryKey() - Web APIs 编辑

The continuePrimaryKey() method of the IDBCursor interface advances the cursor to the to the item whose key matches the key parameter as well as whose primary key matches the primary key parameter.

A typical use case, is to resume the iteration where a previous cursor has been closed, without having to compare the keys one by one.

Calling this method more than once before new cursor data has been loaded - for example, calling continuePrimaryKey() twice from the same onsuccess handler - results in an InvalidStateError being thrown on the second call because the cursor’s got value flag has been unset.

This method is only valid for cursors coming from an index. Using it for cursors coming from an object store will throw an error.

Note:

Syntax

cursor.continuePrimaryKey(key, primaryKey);

Parameters

key

The key to position the cursor at.

primaryKey

The primary key to position the cursor at.

Exceptions

This method may raise a DOMException of one of the following types:

Example

here’s how you can resume an iteration of all articles tagged with "javascript" since your last visit:

let request = articleStore.index("tag").openCursor();
let count = 0;
let unreadList = [];
request.onsuccess = (event) => {
    let cursor = event.target.result;
    if (!cursor) { return; }
    let lastPrimaryKey = getLastIteratedArticleId();
    if (lastPrimaryKey > cursor.primaryKey) {
      cursor.continuePrimaryKey("javascript", lastPrimaryKey);
      return;
    }
    // update lastIteratedArticleId
    setLastIteratedArticleId(cursor.primaryKey);
    // preload 5 articles into the unread list;
    unreadList.push(cursor.value);
    if (++count < 5) {
      cursor.continue();
    }
};

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Using IndexedDB
• Starting transactions: IDBDatabase
• Using transactions: IDBTransaction
• Setting a range of keys: IDBKeyRange
• Retrieving and making changes to your data: IDBObjectStore
• Using cursors: IDBCursor
• Reference example: To-do Notifications (view example live.)