Js download file from indexeddb

February 28th, at Robert Nyman Thanks for asking! March 6th, at Robert Nyman Thanks for the tip! March 14th, at Robert Nyman Thanks! April 24th, at Robert Nyman Thanks, glad you liked it! May 20th, at Robert Nyman Good question! If you come up with something clever, please let us know!

May 22nd, at Mitchell Hello Robert, Thank you for demo. Do you know why I get a security error if I load an image from my Web server?

Why would revokeObjectURL throw that error for you? July 31st, at Sam How much data can be stored on client side using indexedDB? August 27th, at Robert Nyman It is dependent on the web browser, but generally at least 50 MB. September 25th, at Ruben Hi! September 26th, at Robert Nyman Great! IndexedDB storing and retrieving files. This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below.

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This comment has been minimized. Sign in to view. Copy link Quote reply. Your own use case may look like the above gist that. This would have been better without the "image" parts. Sign up for free to join this conversation on GitHub. Learn more. Import and Export Indexeddb data Ask Question. Asked 8 years, 4 months ago. Active 1 year ago. Viewed 15k times. Add a comment. Active Oldest Votes.

For import, you can just accept a JSON file, parse it, and add it to the database. JustinEmery, have you done any testing on large datasets for s of thousands of rows or maybe a million? Vass no. The module uses JSON. This design forces you to think about and handle errors, but you can always add a catchall error handler to the database if fine-grained error handling is too cumbersome.

If you don't handle an error event or if you call abort on the transaction, then the transaction is rolled back and an abort event is fired on the transaction. Otherwise, after all pending requests have completed, you'll get a complete event. If you're doing lots of database operations, then tracking the transaction rather than individual requests can certainly aid your sanity.

Now that you have a transaction, you'll need to get the object store from it. Transactions only let you have an object store that you specified when creating the transaction.

Then you can add all the data you need. The result of a request generated from a call to add is the key of the value that was added. So in this case, it should equal the ssn property of the object that was added, since the object store uses the ssn property for the key path. Note that the add function requires that no object already be in the database with the same key. If you're trying to modify an existing entry, or you don't care if one exists already, you can use the put function, as shown below in the Updating an entry in the database section.

Now that the database has some info in it, you can retrieve it in several ways. First, the simple get. You need to provide the key to retrieve the value, like so:. That's a lot of code for a "simple" retrieval. Here's how you can shorten it up a bit, assuming that you handle errors at the database level:. See how this works? Since there's only one object store, you can avoid passing a list of object stores you need in your transaction and just pass the name as a string.

Also, you're only reading from the database, so you don't need a "readwrite" transaction. Calling transaction with no mode specified gives you a "readonly" transaction. Another subtlety here is that you don't actually save the request object to a variable. Since the DOM event has the request as its target you can use the event to get to the result property.

Note that you can speed up data access by limiting the scope and mode in the transaction. Now we've retrieved some data, updating it and inserting it back into the IndexedDB is pretty simple. Let's update the previous example somewhat:. So here we're creating an objectStore and requesting a customer record out of it, identified by its ssn value We then put the result of that request in a variable data , update the age property of this object, then create a second request requestUpdate to put the customer record back into the objectStore , overwriting the previous value.

Note: In this case we've had to specify a readwrite transaction because we want to write to the database, not just read from it. Using get requires that you know which key you want to retrieve. If you want to step through all the values in your object store, then you can use a cursor. Here's what it looks like:. The openCursor function takes several arguments. First, you can limit the range of items that are retrieved by using a key range object that we'll get to in a minute.

Second, you can specify the direction that you want to iterate. In the above example, we're iterating over all objects in ascending order. The success callback for cursors is a little special. The cursor object itself is the result of the request above we're using the shorthand, so it's event.

Then the actual key and value can be found on the key and value properties of the cursor object. If you want to keep going, then you have to call continue on the cursor. When you've reached the end of the data or if there were no entries that matched your openCursor request you still get a success callback, but the result property is undefined.

One common pattern with cursors is to retrieve all objects in an object store and add them to an array, like this:. Note: Alternatively, you can use getAll to handle this case and getAllKeys. The following code does precisely the same thing as above:.

There is a performance cost associated with looking at the value property of a cursor, because the object is created lazily. When you use getAll for example, the browser must create all the objects at once. If you're just interested in looking at each of the keys, for instance, it is much more efficient to use a cursor than to use getAll. If you're trying to get an array of all the objects in an object store, though, use getAll.

Whether this is a good idea for privacy is a different question, and outside the scope of this article. If you need to look up a customer by name, however, you'll need to iterate over every SSN in the database until you find the right one.

Searching in this fashion would be very slow, so instead you can use an index. The "name" index isn't unique, so there could be more than one entry with the name set to "Donna". In that case you always get the one with the lowest key value. If you need to access all the entries with a given name you can use a cursor.

You can open two different types of cursors on indexes. A normal cursor maps the index property to the object in the object store. A key cursor maps the index property to the key used to store the object in the object store. The differences are illustrated here:. If you would like to limit the range of values you see in a cursor, you can use an IDBKeyRange object and pass it as the first argument to openCursor or openKeyCursor.

You can make a key range that only allows a single key, or one that has a lower or upper bound, or one that has both a lower and upper bound. The bound may be "closed" i.

Here's how it works:. Sometimes you may want to iterate in descending order rather than in ascending order the default direction for all cursors.