Why restrict to 54-bit signed integers? Is there some common language I’m not thinking of that has this as its limit?
Edit: Found it myself, it’s the range where you can store an integer in a double precision float without error. I suppose that makes sense for maximum compatibility, but feels gross if we’re already identifying value types. I don’t come from a web-dev/js background, though, so maybe it makes more sense there.
I didn’t think you realize just how much code is written in JavaScript these days.
Why restrict to 54-bit signed integers?
Because
numberis a double, and IEEE754 specifies the mantissa of double-precision numbers as 53bits+sign.Meaning, it’s the highest integer precision that a double-precision object can express.
I suppose that makes sense for maximum compatibility, but feels gross if we’re already identifying value types.
It’s not about compatibility. It’s because JSON only has a
numbertype which covers both floating point and integers, andnumberis implemented as a double-precision value. If you have to express integers with a double-precision type, when you go beyond 53bits you will start to experience loss of precision, which goes completely against the notion of an integer.
A summary:
An old proposal (2015, not sure why OP posted it now), that basically proposes to put some more standards and limitations around JSON formatting to make it more predictable. Most of it seems pretty reasonable:
- Must be UTF-8 encoded and properly escape Unicode characters
- Numbers must respect the JavaScript number Type and it’s limitations (i.e. max magnitude of an int etc.)
- Objects can’t have duplicate keys
- The order of keys in objects does not matter
- A JSON file does not need to have a top level object or array, it can be any JSON value (i.e. just a string or a number is still valid JSON).
- It proposes that when processing JSON, any unrecognized keys should be ignored rather than errored
It recommends:
- Specific formats for date-time data
- That binary data be stored as a bas64url string
Honestly, the only part of this I dislike is the order of keys not mattering. I get that in a bunch of languages they use dictionary objects that don’t preserve order, but backend languages have a lot more headroom to adapt and create objects that can, vs making a JavaScript thread loop over an object an extra time to reorder it every time it receives data.
Personally, I prefer duplicate keys to be eaten by the parser but I can see how it’d be beneficial to prevent them.
I’m honestly unsure if they intend the ‘must-ignore’ policy to mean to eat duplicate keys without erroring, or just to eat keys that are unexpected based on some contract or schema…
Posting something like this — assuming you actually read the thing and found it to be valuable in some way — without any summary text whatsoever is just lazy af; it’s a low quality effort, and you should feel bad about it.
Ok.
