a_reg = {
if (regions_btn == 0) return 'En attente...'
let regs_features = a_com_topo.objects.a_reg2021_2154.geometries
.map ( r => [r.properties.reg,
topojson.merge(a_com_topo,
a_com_topo.objects.a_com2021_2154.geometries
.filter(d => d.properties.reg === r.properties.reg))] )
.map(d => ({type:'Feature', properties:d[0], geometry:d[1]}))
return {type: "FeatureCollection", features: regs_features}
}