根据两点经纬度计算两点间距离 js

　　　　　　　　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
                }
            },