I'm still struggling my way through learning IndexedDB. I'm going to post examples as I learn - but as a warning - please consider anything I post as potentially wrong, misleading, and dangerous to the fabric of the universe.
In today's post - I simply wanted to create an objectstore (again, think of a table) with an autogenerating key. The (mostly) incredibly useful MDN documentation talks a bit about how you can either provide a key manually or use a key generator. However it doesn't explain how you actually use a key generator. This seems to imply that indexeddb has a way to allow you to write your own logic to create keys. For example, perhaps by combining a few properties, or perhaps by simply counting the existing objects and adding one to it. I'm still not sure if that actually exists. However, there is a simpler way of doing it.
When you create your object store, you provide a name and a map of options. One option is the keypath, which is basically the property of your data expected to hold a value. The second option is a key called autoIncrement. This defaults to false, but if you set it to true, you get nicely autoincrementing keys. Here's an example by itself:
And here is a complete template. Note it also supports a simple button to add data and then dump it to console. Note that adding data currently barfs on Chrome with:
Uncaught Error: DATA_ERR: DOM IDBDatabase Exception 5
Which according to the MDN reference is "Data provided to an operation does not meet requirements." If I had to guess, I'd say maybe Chrome isn't supporting the auto generated key. (Note - I just did a test and confirmed this. Well, I'll be focusing then on Firefox, which seems to be more to spec.) For a complete example, see the code below.