Merging JSON with array to create new file - json

Question

I am trying to make a map of the U.S. with Mapbox that shows median home price by county. I have a .json file that contains all the counties and is already accepted by Mapbox tileset -
{
"type": "Topology",
"transform": {
"scale": [
0.035896170617061705,
0.005347309530953095
],
"translate": [
-179.14734,
17.884813
]
},
"objects": {
"us_counties_20m": {
"type": "GeometryCollection",
"geometries": [
{
"type": "Polygon",
"arcs": [],
"id": "0500000US01001"
},
{
"type": "Polygon",
"arcs": [],
"id": "0500000US01009"
},
{
"type": "Polygon",
"arcs": [],
"id": "0500000US01017"
},
{
"type": "Polygon",
"arcs": [],
"id": "0500000US01021"
}
]
}
}
}
Basically, it's a json file with "type" (Polygon), "arcs" (to map the county), and "id", which is an ID for the county.
This is great and accepted by Mapbox Tilesets to give me a visualization by county, but I need to add in median home price by county (in order to get colors by county, based on price).
I have a second json file that is more like an array, which has
[
{
"0500000US01001": 51289.0,
"0500000US01009": 46793.0,
"0500000US01017": 39857.0,
"0500000US01021": 48859.0
}
]
and so on, but basically it has the ID -> median home price per county. The ID's are the same between these 2 files, and of the same quantity. So I need get a 3rd json file out of these, which has "type", "arcs", "id", and "PRICE" (the addition).
These files are huge - any suggestions? I tried using jq but received an error that
jq: error ... object ({"type":"To...) and array ([{"0500000U...) cannot be multiplied
Thanks in advance!

Answer 1

A straightforward approach would be saving the second file into a variable and using it as a reference while updating the first file. E.g:
jq 'add as $prices | input
| .objects.us_counties_20m.geometries[] |= . + {PRICE: $prices[.id]}' file2 file1
add can be substituted with .[0] if the array in file2 contains only one object.
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