获取两地的之间距离

// 经纬度转换成三角函数中度分表形式。
function rad(d) {
            return d * Math.PI / 180.0; 
        }


        // 根据经纬度计算距离，参数分别为第一点的纬度，经度；第二点的纬度，经度
        function getDistance(lat1, lng1, lat2, lng2) {

            var radLat1 = rad(lat1);
            var radLat2 = rad(lat2);
            var a = radLat1 - radLat2;
            var b = rad(lng1) - rad(lng2);
            var 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; // EARTH_RADIUS;
            s = Math.round(s * 10000) / 10000; //输出为公里

            var distance = s;
            var distance_str = "";

            if (parseInt(distance) >= 1) {
                distance_str = distance.toFixed(1) + "km";
            } else {
                distance_str = distance * 1000 + "m";
            }
            return distance_str;
        }
        let a = getDistance(113.420329,23.111403,113.430462,23.10746)
        console.log(a)