Unable to define a variable of type: `number` or `null`
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- TypeScript
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Description
I have a problem with the following expression:
```
"line-color": [
'let',
'aVsB',
[
'case',
['all', ['has', 'a'], ['has', 'b']],
['-', ['get', 'a'], ['get', 'b']],
null,
],
[
'case',
['!=', ['var', 'aVsB'], null],
[
'case',
['>', ['var', 'aVsB'], 0],
'blue',
'red',
],
"black",
],
],
```
I somehow need to indicate that the `aVsB` value is not valid. Is it possible to define a variable `aVsB` that can be either `number` or `null`? Then I'm going to compare it with `null` to display the necessary color.
Not working:
https://jsfiddle.net/NameFILIP/oLw1ysjm/34/
Workaround 1:
https://jsfiddle.net/NameFILIP/oLw1ysjm/31/
Workaround 2:
https://jsfiddle.net/NameFILIP/oLw1ysjm/36/
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the expression in the issue and compare the three linked jsfiddle reproductions, including both listed workarounds. Trace how the expression handles a variable assigned either a number or null, then define completion as consistent support for the requested comparison without breaking the demonstrated color expression.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, typescript
- Domain
- frontend, web-dev
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100