getDistance(lat1, lng1, lat2, lng2) {

                let radLat1 = lat1 * Math.PI / 180.0;

                let radLat2 = lat2 * Math.PI / 180.0;

                let a = radLat1 - radLat2;

                let b = lng1 * Math.PI / 180.0 - lng2 * Math.PI / 180.0;

                let s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2) + Math.cos(radLat1) * Math.cos(radLat2) * Math

                    .pow(Math.sin(b / 2), 2)));

                s = s * 6378.137;

                s = Math.round(s * 10000) / 10000;

                let distance = s.toString();

                let distance_str = "";

                distance = distance.substring(0, distance.indexOf('.') + 2);

                if (parseInt(distance) >= 1) {

                    distance_str = distance + "km";

                    return distance_str

                } else {

                    distance_str = (distance * 1000) + "m";

                    return distance_str

                }

            },