Allow importing and exporting to JSON

[cooperka]

Awesome library, love the unit tests! I'm using it for caching web response data in a mobile app, and I find import/export to be valuable for saving to disk and restoring the cache later (for example, if you kill the app and then open it again, restore the offline data in case there's no internet anymore).

exportJson = function()

• Returns a JSON string representing all the cache data
• Any timeoutCallbacks will be ignored, as these can't easily be serialized

importJson = function(json: string, options: { skipDuplicates: boolean })

• Merges all the data from a previous call to export into the cache
• Any existing entries before an import will remain in the cache
• Any duplicate keys will be overwritten, unless skipDuplicates is true
• Any entries that would have expired since being exported will expire upon being imported (but their callbacks will not be invoked)
• Available options:
  • skipDuplicates: If true, any duplicate keys will be ignored when importing them. Defaults to false.
• Returns the new size of the cache

[katzgrau]

I was going to submit a PR for the same thing — I think this would be extremely helpful.

I have an app that relies heavily on memory-cache, and deploys wipe the cache, obviously.

I'm also sure that some apps running under supervisor or nodemon occasionally crash on some unexpected data, and could use this to keep things moving along smoothly.

[cooperka]

@ptarjan is this something you'd consider merging? Let me know if there's anything I can improve.

[ptarjan]

Yeah this sounds reasonable. I might debate on the names and API format once I see it but the overall shape seems broadly useful.

…

On Mon, Feb 27, 2017 at 1:20 PM Kevin Cooper ***@***.***> wrote: @ptarjan <https://github.com/ptarjan> is this something you'd consider merging? Let me know if there's anything I can improve. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#83 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AACcz7ANhU1XA0V19xwgJCoSDK-JyKyyks5rgz43gaJpZM4MCVAu> .

[katzgrau]

Just kidding, but any potential ETA?

[ptarjan]

It was unintuitive to me that 'Nan' - Date.now() == Nan? Either add a separate if or a comment

[cooperka]

Agreed, I'll make this more clear.

[ptarjan]

this seems weird to silently ignore things that already exist. I'd throw by default and add a tri-state option if people want to skip duplicates, overwrite, or the default of throw.

[cooperka]

Actually this is deleting the key rather than ignoring it. If you import a key that has expired, it will cause the key to be removed from the existing cache, as would have happened automatically.

It's a good idea to add an option to skip duplicates instead of overwriting -- I'll do that soon. I don't think throwing makes sense though, since it's a perfectly valid key, it's just supposed to have expired. Thoughts?

[cooperka]

@ptarjan thanks for the feedback, it's updated now.

[cooperka]

@ptarjan ping :)

[sebyddd]

👍

[ptarjan]

Sorry to ask this, but #85 submitted before you. Can you rebase on it and match the style they introduced? Thanks.

[cooperka]

@ptarjan done!