SSCCE
result = Json.Decode.decodeValue (Json.Decode.dict Json.Decode.string) jsValue
when jsValue has been created in JavaScript using Object.create(null) and sent through flags or a port.
Attempting the decoding above results in a runtime exception with this error:
Uncaught TypeError: value.hasOwnProperty is not a function
at _Json_runHelp (VM37 workspace:1461)
at _Json_runHelp (VM37 workspace:1478)
at Function.f (VM37 workspace:1400)
at A2 (VM37 workspace:56)
at $author$project$Main$init (VM37 workspace:10540)
at VM37 workspace:8540
at VM37 workspace:20
at _Platform_initialize (VM37 workspace:1877)
at VM37 workspace:3973
at Object.init (VM37 workspace:20)
I created an Ellie here that you can interact with: https://ellie-app.com/8ZWrTfBzWRZa1
Additional Details
- Elm: 0.19.1
- elm/json: 1.1.3
- Browser: Brave
Object.create(null) is sometimes used to create a JavaScript dictionary . The difference with {} is that {} contains fields from the Object prototype, where Object.create(null) has no prototype and no fields at all.
> ({}).toString
[Function: toString]
> Object.create(null).toString
undefined
This distinction, at least in JavaScript, can be important when you use this value as a set and only care about whether the field exists.
This distinction is irrelevant when decoding, but this runtime error makes it impossible to send values that in JS-land needed to be created this way without somehow cloning them beforehand.
SSCCE
when
jsValuehas been created in JavaScript usingObject.create(null)and sent through flags or a port.Attempting the decoding above results in a runtime exception with this error:
I created an Ellie here that you can interact with: https://ellie-app.com/8ZWrTfBzWRZa1
Additional Details
Object.create(null)is sometimes used to create a JavaScript dictionary . The difference with{}is that{}contains fields from the Object prototype, whereObject.create(null)has no prototype and no fields at all.This distinction, at least in JavaScript, can be important when you use this value as a set and only care about whether the field exists.
This distinction is irrelevant when decoding, but this runtime error makes it impossible to send values that in JS-land needed to be created this way without somehow cloning them beforehand.