countryNameForCoord.js

// depends on turf and having a copy of the countries.gejson file for the value of the countryOutlines
// see: https://github.com/johan/world.geo.json as one source
    
    findCountryName (latlon) {
        var features, i, j, poly;
        var point1 = turf.point([latlon[1], latlon[0]]);

        if (this.countryOutlines) {
            features = this.countryOutlines.features;
            for (i=0; i<features.length; i++) {

                 if ( features[i].geometry.type === 'MultiPolygon' ) {
                     for (j=0; j<features[i].geometry.coordinates.length; j++) {
                          poly = turf.polygon(features[i].geometry.coordinates[j]);
                          try {
							  if (turf.inside(point1, poly)) {
								 return features[i].properties.name;
							 }
						  } catch (e) {
						      // typically happens due to a geometry issue
						      console.error(e, features[i].id, j);
						  }
                     }
                 } else if ( features[i].geometry.type === 'Polygon' ) {
                     poly = turf.polygon(features[i].geometry.coordinates[0]);

                     if (turf.inside(point1, poly)) {
                         return features[i].properties.name;
                     }
                 } else {
                     console.error('unknown geometry type: ' + features[i].geometry.type);
                 }
            }
        }
    }