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Announcing Scala.js v0.1

scala-lang.org

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Re: Announcing Scala.js v0.1

#11

Post by chimeracoder »

smenko wrote: post #9
jakozaur wrote: post #5

Earlier quoted context omitted.

Parsing JSON in Scala is very easy with lift-json: https://github.com/lift/lift/tree/master/framework/lift-base...

Is this supposed to be ironic? Considering JSON.parse( {a: "B"} )

JSON is always going to be a bit more difficult to parse in statically typed languages than dynamically typed ones.

The amusing part is that most APIs use JSON as if it were statically typed - except for null/undefined, very few APIs return values of more than one possible type for a given key[0].

It doesn't always have to be so bad, though, even in statically typed languages. For example, I created a tool in Go to automatically generate struct definitions, given an example JSON response: https://github.com/ChimeraCoder/gojson

In the time that I've been using it (since last December), I don't think I've run into any issues with an API returning an incorrect type for a particular key[1].

[0] For the record, I'm not complaining. The alternative would be a nightmare to deal with. [1] Though they do sometimes return a different object altogether; this is an issue regardless of which type system you use.

Re: Announcing Scala.js v0.1

#13

Post by saryant »

jakozaur wrote: post #5
leokun wrote: post #2

I wonder how complicated it is to parse JSON in Scala.js. It's pretty involved in regular Scala and incredibly easy in JavaScript, so what's it like in Scala.js?

Parsing JSON in Scala is very easy with lift-json: https://github.com/lift/lift/tree/master/framework/lift-base...

There's also Play-Json, Spray-Json, various wrappers for Jackson and a few others I don't remember. We use Play-Json and its macros a lot at the company I work for and I contributed a performance fix for it a while back. I wouldn't consider Play's JSON inception to be "pretty involved" at all if you're using case classes.

http://www.playframework.com/documentation/2.2.x/ScalaJson

https://github.com/spray/spray-json

Re: Announcing Scala.js v0.1

#14

Post by memracom »

Too bad that there is not more effort on Scala.NET instead of this. Lots of people are comfortable with writing Javascript in the browser so all of these compilers emitting Javascript end up being little more than a technology demo. But Scala on the .NET vm would really fill a gap.

Re: Announcing Scala.js v0.1

#15

Post by leokun »

jakozaur wrote: post #5
leokun wrote: post #2

I wonder how complicated it is to parse JSON in Scala.js. It's pretty involved in regular Scala and incredibly easy in JavaScript, so what's it like in Scala.js?

Parsing JSON in Scala is very easy with lift-json: https://github.com/lift/lift/tree/master/framework/lift-base...

I use argonaut.io and it isn't really hard so much as tedius compared to JavaScript or Python.

Re: Announcing Scala.js v0.1

#16

Post by leokun »

chimeracoder wrote: post #11
smenko wrote: post #9

Earlier quoted context omitted.

Is this supposed to be ironic? Considering JSON.parse( {a: "B"} )

JSON is always going to be a bit more difficult to parse in statically typed languages than dynamically typed ones. The amusing part is that most APIs use JSON as if it were statically typed - except for null/undefined, very few APIs return values of more than one possible type for a given key[0]. It doesn't always have to be so bad, though, even in statically typed languages. For example, I created a tool in Go to a…

Given that it uses reflect I bet your library very slow. I wonder how it compares to parsing JSON in Python or node.js.

> except for null/undefined,

That's not a small issue.

Not only do JSON responses for API's vary a great deal from request to request, some handle errors without HTTP response code's. So the JSON you get back can be very different then you might expect otherwise.

Re: Announcing Scala.js v0.1

#18

Post by chimeracoder »

leokun wrote: post #16
chimeracoder wrote: post #11

Earlier quoted context omitted.

JSON is always going to be a bit more difficult to parse in statically typed languages than dynamically typed ones. The amusing part is that most APIs use JSON as if it were statically typed - except for null/undefined, very few APIs return values of more than one possible type for a given key[0]. It doesn't always have to be so bad, though, even in statically typed languages. For example, I created a tool in Go to a…

Given that it uses reflect I bet your library very slow. I wonder how it compares to parsing JSON in Python or node.js. > except for null/undefined, That's not a small issue. Not only do JSON responses for API's vary a great deal from request to request, some handle errors without HTTP response code's. So the JSON you get back can be very different then you might expect otherwise.

> Given that it uses reflect I bet your library very slow.

Look carefully - what I wrote is not a library; it's a standalone binary. It's run exactly once, when you write the code, so speed isn't an issue.

> That's not a small issue.

Depends on the language. In Go, it's very easy to allow a JSON value to be null and/or undefined by making the value it unmarshals to a pointer (which you should be doing already anyway).

What's harder (in most languages, not just Go) is dealing with a value that could be (say) either a string, or a 64-bit int. Or, worse, a string whose value just happens to be a 64-bit number. When that happens (which is thankfully rare), it breaks the "JSON should be self-documenting" motto.

> So the JSON you get back can be very different then you might expect otherwise.

This is an issue no matter what language you use. You have to know what the set of possible response structures is in order to know what keys to query/access.

Re: Announcing Scala.js v0.1

#19

Post by wodenokoto »

As someone who doesn't really know anything about scala, why is this a cool thing?

While such an early release is definitely aimed at scala enthusiast, I'd still like a sales pitch for the rest of us.

Re: Announcing Scala.js v0.1

#20

Post by tree_of_item »

leokun wrote: post #2

I wonder how complicated it is to parse JSON in Scala.js. It's pretty involved in regular Scala and incredibly easy in JavaScript, so what's it like in Scala.js?

It's exactly the same as in JavaScript: JSON.parse(...)

Scala has Dynamic types for when you want to play rough like that.

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