How to get property from TopoJSON file using D3.js version 7?

I have the following TopoJSON file:

{
    "type":"Topology",
    "arcs":[...],
    "transform":{
        "scale":[...],
        "translate":[...]
    },
    "objects":{
        "BRGR":{
            "type":"GeometryCollection",
            "geometries":[
                {
                "arcs":[[0,1,2]],
                "type":"Polygon",
                "properties":{
                    "codarea":"1"
                }
            },
            {
                "arcs":[[[3,4,5,-1]],[[6]]],
                "type":"MultiPolygon",
                "properties":{
                    "codarea":"2"
                }
            },
            {
                "arcs":[[[-5,7,8,9]],[[10]]],
                "type":"MultiPolygon",
                "properties":{
                    "codarea":"3"
                }
            },
            {
                "arcs":[[11,12,-9]],
                "type":"Polygon",
                "properties":{
                    "codarea":"4"
                }
            },
            {
                "arcs":[[-13,13,-2,-6,-10]],
                "type":"Polygon",
                "properties":{
                    "codarea":"5"
                }
            }]
        }
    }
}

I’m able to log it in the console using:

console.log(topology.objects.BRGR);

Having the following expected result:

{type: 'GeometryCollection', geometries: Array(5)}
  geometries: Array(5)
    0: {arcs: Array(1), type: 'Polygon', properties: {…}}
    1: {arcs: Array(2), type: 'MultiPolygon', properties: {…}}
    2: {arcs: Array(2), type: 'MultiPolygon', properties: {…}}
    3: {arcs: Array(1), type: 'Polygon', properties: {…}}
    4: {arcs: Array(1), type: 'Polygon', properties: {…}}
    length: 5
    [[Prototype]]: Array(0)
    type: "GeometryCollection"
    [[Prototype]]: Object

I’m unable to log the value of codarea directly. What brought me the closest solution was:

console.log(topojson.feature(topology, topology.objects.BRGR).features);

I’ve tried a lot of possibilities such as:

console.log(topojson.feature(topology, topology.objects.BRGR).features.properties.codarea);

without success. I have no idea what we have to do to get this value.
Actually I’d like to use it in a D3.js script to modify the color of the map on the fly.
The code is:

// svg general properties
var width = 1024,
    height = 512;

// set projection
// https://github.com/d3/d3-geo#projections
var projection = geo.geoCylindricalEqualArea() // projeção cilíndrica equivalente de Lambert
    .parallel(32)
    .scale(670)
    .rotate([45,14,0]);

// color scheme
var colorScheme = d3.schemeBlues[5];
colorScheme.unshift("#eeeeee")
var colorScale = d3.scaleThreshold()
    .domain([0, 1])
    .range(colorScheme);

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);

var path = d3.geoPath()
    .projection(projection);

var g = svg.append("g");

// load and display the map
d3.json("map.json").then(function(topology) {

    g.selectAll("path")
        .data(topojson.feature(topology, topology.objects.BRGR).features)
        .enter().append("path")

//---->
//----> THIS IS WHERE CODAREA WOULD MODIFY COLOR
//---->
        .style("fill", function (event, d) {
            // pull data for this state
            d.codarea = ???;
            // set the color
            return colorScale(d.codarea);
        })

        .attr("d", path)
});

And the highlighted part I extracted from http://bl.ocks.org/palewire/d2906de347a160f38bc0b7ca57721328 but differently from the source I’m using D3 version 7

//----> MY CODE
//----> THIS IS WHERE CODAREA WOULD MODIFY COLOR
//---->
        .style("fill", function (event, d) {
            // pull data for this state
            d.codarea = ???;
            // set the color
            return colorScale(d.codarea);
        })

And here the original code:

   .attr("fill", function (d){
        // Pull data for this country
        d.total = data.get(d.id) || 0;
        // Set the color
        return colorScale(d.total);
    })

But as I said, I can’t get the proper data from my TopoJSON. How would this be possible, so I can use it in the script?