CODEWITHSUNDEEP
javascriptindexeddb
bsr
bsr

Reputation: 58662

indexeddb: how to get request result and cursor value

Two questions about indexeddb operations.

  1. what is the reliable way to get result from an idb request. I see two froms

var cursor = request.result; W3C

var cursor = event.target.result; MDN

would they give same results always for all requests.

2. is there a value property on cursor retuned by index.openCursor. I see it is used in W3C spec at one place, in a example.

[report(cursor.value.isbn, cursor.value.title, cursor.value.author);][3]

is there a place it say I can use it.

Upvotes: 1

Views: 1248

Answers (1)

buley
buley

Reputation: 29208

1) In general it's all requests that have results. There are different types of requests (such as IDBOpenDBRequest and cursor requests) and various ways to get to objects such as IDBDatabase and IDBObjectStore depending on the request. event.target.result is just one example.

For example:
* An IDBIndex will have an IDBObjectStore at objectStore.
* With an IDBObjectStore you'll find a reference to an IDBTransaction at transaction
* On an IDBTransaction, there will be a db attribute with an IDBDatabase.
* An IDBOpenDBRequest will have its IDBDatabase on the result property

In addition to event.target you'll also find an event.source that carries such objects and references.

Various types of IDB objects can appear as a target, and so the event.target.result will change depending on the method used. It even depends on the callback used: a success callback from a cursor request yields an IDBCursorWithValue as event.target.result (with a request being the target) and nothing on a complete event.

2) In general it's just IDBCursorWithValue requests that have a value. There are various requests that don't yield value, which even include certain types of valueless cursor requests.

Update: A IDBRequest will have a IDBCursorWithValue at request.result and its cursor value is usually (but not always) going to be at request.result.value (with the exception being value-free cursors, which I doubt you'll be using). request is returned by the method synchronously (my preferred method to grab a reference) or obtained via event.target (a little confusing). Check out this method called standardCursor in my library. It's reused by entries.delete, entries.get and entries.update and should point you in the right direction. My lib is literate and implemented to spec w/exception of its webkitGetDatabaseNames support.

Upvotes: 2

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