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Indexeddb: Differences between onsuccess and oncomplete?

I use two different events for the callback to respond when the IndexedDB transaction finishes or is successful:

Let's say... db : IDBDatabase object, tr : IDBTransaction object, os : IDBObjectStore object

tr = db.transaction(os_name,'readwrite');
os = tr.objectStore();

case 1 :

r = os.openCursor();
r.onsuccess = function() {
    if(r.result){
        callback_for_result_fetched();
        r.result.continue;
    } else {
        callback_for_transaction_finish();
    }
}

case 2:

tr.oncomplete = callback_for_transaction_finish();

It is a waste if both of them work similarly. So can you tell me, is there any difference between them?

Answer*

Sorry for raising up quite an old thread, but it's questioning is a good starting point...

I've looked for a similar question but in a bit different use case and actually found no good answers or even a misleading ones.

Think of a use case when you need to make **several writes** into the objectStore of even into several ones. You definitely **don't want** to manage each single write and it's own success and error events. That is the meaning of transaction and this is the (proper) implementation of it for indexedDB:

var trx = dbInstance.transaction([storeIdA, storeIdB], 'readwrite'),
    	storeA = trx.objectStore(storeIdA),
        storeB = trx.objectStore(storeIdB);

trx.oncomplete = function(event) {
            // this code will run only when ALL of the following requests are succeed
            // and only AFTER ALL of them were processed
        };
    	trx.onerror = function(error) {
            // this code will run if ANY of the following requests will fail
            // and only AFTER ALL of them were processed
        };

storeA.put({ key:keyA, value:valueA });
    	storeA.put({ key:keyB, value:valueB });
        storeB.put({ key:keyA, value:valueA });
    	storeB.put({ key:keyB, value:valueB });

Clue to this understanding is to be found in the following statement of W3C [spec][1]:

> To determine if a transaction has completed successfully, listen to the transaction’s **complete event rather than the success event of a particular request**, because the transaction may still fail after the success event fires.

[1]: http://www.w3.org/TR/IndexedDB/#widl-IDBTransaction-oncomplete

Edit Summary*

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just what i was looking for. i assume objectStore.onsuccess, and objectStore.oncomplete can also be used for multi .add, . get, .put, etc... on given objectstore.
– Ryan Sanders
Commented Oct 15, 2016 at 7:39
do you need trx.commit()? And for reading, if I want to do flatmap from multiple stores, should I do it with onSuccess instead? I have a wrapper function to make all of them async functions.
– Pui Ho Lam
Commented Aug 27, 2024 at 18:13
1

@PuiHoLam commit MAY be called but not MUST to (if called will commit the changes immediately, if not - I believe it'll happen at the end of the current microtask, but see more here. Regarding onSuccess vs onComplete - well, it's up to your requirement, either do it in any case or only in success case.
– GullerYA
Commented Aug 28, 2024 at 7:59

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Indexeddb: Differences between onsuccess and oncomplete?

Answer*