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If the property does exist, we ensure that it is an integer with the parseInt function. For in-
stance, if we are passed a number as a string, then we convert it to a number. This is anoth-
er important consideration, since the toObject implementation currently always produces
This is the first time we have seen the native JavaScript parseInt function. Al-
though this is a useful function, it does have its problems. In order to see these
first hand, try the following call:
> parseInt(010)
It will be left to the reader to discover why this returns 8 rather than 10.
Next we create a transaction in the database and add onerror and onsuccess callbacks to it:
var tx = database.transaction([type], "readwrite");
tx.oncomplete = function(event) {
tx.onerror = function(event) {
errorCallback('transaction_error', 'It is not possible to store the object');
We can only access an object store in the context of a transaction. A transaction groups to-
gether a set of operations on one or more object stores. The transaction will auto-commit
once all requests against the transaction have completed.
It is not until the transaction completes that we will notify the client of success. If we noti-
fied the client after the requests had been submitted they might encounter a situation where
they cannot query the object store for the objects. This is because all changes to the object
store will remain hidden from all clients until the transaction commits.
The transaction is specified as a “readwrite” transaction: you must specify this
if you want to modify objects in an object store. The default transaction type is
“read”. It may seem strange that a transaction is required even to read objects.
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