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cloudflare Durable Objects update object value

Halo! I'm recently diving into cloudflare Workers, especially Durable Objects. I could make a simple request which put a js object into the assigned key. Let's say the key is key0, and the put object value is {"fieldA": "val0", "fieldB": "val1"}. In this case, how can i update the field-value of fieldA without removing fieldB? I've tried simply executing put("key0", {"fieldA": "newVal0"}) and it has kept removing {"fieldB": "val1"}.

Of course it is a common behaviour in js operations, but i cannot find out anything like ~["key0"]["fieldA"] = "newVal0" in docs(maybe i'm missing sth). OTL

Hope this question reach to the gurus in the community! Thanks in advance [:

EDIT after the answers:

In theory, it would be wonderful if flare durable objects support and work just like a normal js object. Such possible worker feature feels like a killer app for the cloud db services, since the average cpu time is quite fast and flare also has super low pricing compared to other big bros. If it happens, i would eager to migrate everything into the flare platform [:

Solution

  • Durable Objects' KV storage only supports get and put operations -- it doesn't have any sort of "update". So, you have two options:

    1. get() the key, modify it, and then write the modified version back. This may sound inefficient, but keep in mind that commonly-accessed keys will likely be in in-memory cache. In fact, this get/modify/put implemented in your JavaScript is probably about as fast as any modification operation that Durable Objects itself could possibly implement built-in. That said, you probably don't want to use this approach with large objects, since the whole object has to be written to disk again after every update.

    2. Split your object across multiple keys. E.g. instead of having the key foo map to {"fieldA": "val0", "fieldB": "val1"}, you could have separate keys foo:fieldA and foo:fieldB. Note that you can fetch all the keys at once using storage.list({prefix: "foo:"}). This approach is not as convenient but allows each field to be written separately to disk.