GeoJSON polygons on import into ArcGIS Web are always solid filled, instead of the transparency/opacity styles we set for geoJson - geojson

Question

I've been playing with GeoJSON only recently, and was wanting to request some assistance on the below:
We save the graphitems (polygon rings, etc), from the web maps.
We then convert it to a GeoJSON file for export, along with styles for transparency/opacity (see code further below).
We then send the exported GeoJSON file for import into ArcGIS.
The file is imported successfully, but the, colour or transparency/opacity is not being set, it defaults to 20% opacity.
Is there a way to honour the transparency/opacity for GeoJSON imports into ArcGIS?
Am I setting up the styles incorrectly in the GeoJSON file?
Sample GeoJson file is as per below:
{
"type": "FeatureCollection",
"crs": {
"type": "name",
"properties": {
"name": "EPSG:3857"
}
},
"features": [
{
"type": "Feature",
"geometry": {
"type": "Polygon",
"coordinates": [
[
[
15576024.93758691,
-4055443.47590715
],
[
15576028.52057261,
-4055971.3691337
],
[
15576624.49052747,
-4055960.6201765984
],
[
15576618.518884636,
-4055442.281578583
],
[
15576024.93758691,
-4055443.47590715
]
]
]
},
"properties": {
"id": 13,
"centerPoint": [
-34.20013348612295,
139.9245056104621
],
"address": "Golden Heights, South Australia",
"title": "Golden Heights, South Australia",
"area": 21.232800390625002
},
"style": {
"fill": "blue",
"stroke-width": "3",
"fill-opacity": 0.5
}
}
]
}
Any help on the above would be much appreciated.
Thanks.

Answer 1

Esri layers use the Renderer property to determine how to render features. If you're looking for a generic solution that will work with any geojson, I'm not sure there's an easy way to transform svg-style css classes into an esri renderer. For your case, it looks like you need a SimpleRenderer whose symbol is a SimpleFillSymbol. I don't think there's a shortcut to use css properties from your JSON to tell the api how to create a renderer. This could be a great idea for a plugin, but on the other hand, a small list of simple css classes doesn't have the same capacity to render features at the level of complexity that a Renderer allows for, so I'm not sure how you could even map those css properties to the renderer propeties.
I would also try asking this question on esri's geonet forum - that forum has way more knowledge and activity when it comes to the arcgis js api than SO does.