[Reactive] how to pass Null input to Javascript as undefined

Ricardo Neto

Rank: #5167

[Reactive] how to pass Null input to Javascript as undefined

Question

JavaScript

Reactive

Front-end

Application Type

Reactive

Platform Version

11.10.0 (Build 22422)

I have a client action with multiple inputs and a JS "action", I want some of the inputs to be optional, but, when passing them as JS inputs, for instance a integer would pass 0 as NullIdentifier(). What I want is this input parameter to be interpreted as undefined by JS instead of 0.

Is there any way to do this?

on 2020-11-17

Mikko Nieminen

Rank: #238

Hi,

If you need to differentiate between null and zero/empty/true/false integer/text/date/boolean values, I'd double up on inputs to JS action:
- input1 (int)
- input2 (int)

would then become:
- input1 (int)
- input1_hasvalue (bool)
- input2 (int)
- input2_hasvalue (bool)

Which is basically introducing a concept for "nullable datatype". Inside your JS action (where a concept for null exists) , you can then set/override variables based on this "doubled" _hasvalue input. It's extra logic, but necessary with the platform.

Whenever there are lots of variables, I'd also probably lean towards structures and json serialization / deserialization so the interfaces between OS and JS code stay a bit cleaner.

on 2020-11-17

1 reply

on 2020-11-17

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Ricardo Neto

Rank: #5167

Yeah, that is an unhandsome solution, let's say :p
But I can understand this is a workaround caused by the limitations of the platform

Even though is not ideal, json serialization + javascript json.parse() it's an acceptable one, because we can discard default values and those would be undefined in js.

Also tried with the conversion to object data type, something like:

client action inputs:
some_input_int (int)

js input:
some_input_obj (object)

js assignment:
some_input_obj = if(some_input_int <> NullIdentifier(), ToObject(some_input), NullObject())

If you don't pass anything (NullIdentifier()) it would be null, as expected, but if you pass 0 it would be null as well, and that's a problem.

I think there shouldn't exist a equivalence relation between 0 and NullIdentifier(), in some cases NullIdentifier() could be interpreted as 0, but 0 shouldn't be equal to NullIdentifier() when making a comparison, but that's another discussion...

on 2020-11-17

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[Reactive] how to pass Null input to Javascript as undefined