find point inside feature using turf

js

for (var i = 0; i < geojsontest["features"].length; i++) {
       var poly = geojsontest["features"][i]["geometry"];
       var isInside1 = turf.inside(pt1, poly);
       if(isInside1){
            console.log(geojsontest["features"][i]["properties"]["letter"]);
       }
}