[erlang-questions] New project: ZJ - A tiny JSON encoder/decoder

Whealy, Chris chris.whealy@REDACTED
Wed Jun 27 10:43:39 CEST 2018

Allow me to elaborate on your point Michael (also without getting philosophical).

In JavaScript null and undefined are identifiably distinct datatypes that serve specific purposes:

  *   null - This variable specifically has no value
  *   undefined - The value of this variable is indeterminate (I.E. identifiably different from null)

Although the atom null has no special meaning in Erlang, it does when mapped to JavaScript null; therefore to maintain accuracy, Erlang devs who also work in JavaScript should understand and preserve this semantic difference.  Likewise with Erlang undefined mapping to JavaScript undefined.

Therefore, I submit that this semantic difference should be persevered when mapping from Erlang to JavaScript, otherwise data loss will occur, particularly when mapping from JavaScript back to Erlang.

Erlang    -> JavaScript
null      -> null
undefined -> undefined

JavaScript -> Erlang
null       -> null
undefined  -> undefined

This part of the mapping table at least should be bijective.

Chris Whealy
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On 27 Jun 2018, at 08:42, Michael Nisi <michael.nisi@REDACTED<mailto:michael.nisi@REDACTED>> wrote:

Here’s how v8::JSON, the JSON parser in Node’s JavaScript engine, does it:

JSON.stringify({ name: null })
JSON.stringify({ name: undefined })
JSON.stringify({ name: 'Lionel' })

JSON.parse('{ "name": null }').name

JavaScript differentiates between null and undefined, without wanting to get philosophical here.


On 27. Jun 2018, at 09:21, zxq9@REDACTED<mailto:zxq9@REDACTED> wrote:

Erlang -> JSON
- true      -> true
- false     -> false
- undefined -> null
- Atom      -> String

JSON -> Erlang
- true  -> true
- false -> false
- null  -> undefined

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