MessagePack: like JSON, but fast and small

Re:MessagePack: like JSON, but fast and small by HereBeBeasties on Wednesday March 11, 2020 @03:42AM (#22543903)

What the original poster means is that if I go JSON.parse(...) then how does that know to give me an object with a Date type instead of a Number? Answer: It can't.

This is a frequent gotcha with Typescript, where even if your type is declared with a Date field, Javascript won't care when it deserializes it, as that type information is all erased and not available at runtime.

(Also, Number in JS being floating point and all, it lacks the integer precision for high resolution timestamps - if you start serialising 64 bit timestamps and expect a JS-style runtime to do good things with them it doesn't end well.)

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Re:MessagePack: like JSON, but fast and small by a1369209993 on Wednesday March 11, 2020 @03:00PM (#22549142)

> how does that know to give me an object with a Date type instead of a Number

Ah, thanks, that makes sense; I'd forgotten that Javascript had a built-in Date type. (Strictly speaking, then, you ought to be able to write something like `{"time":new Date(...)}`, but that obviously doesn't work in practice.)

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Re:MessagePack: like JSON, but fast and small by eyelidlessness on Wednesday March 11, 2020 @03:10PM (#22549281)

Since Typescript is mentioned, might as well mention the awesome io-ts[1] library. It gives you both runtime validation and static type safety with very simple syntax.

[1]: https://github.com/gcanti/io-ts

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