JS経度緯度距離計算コード共有

 GetDistance:function(lat1, lng1, lat2, lng2, len_type = 2, decimal = 2)  
    {  
       var radLat1 = lat1 * Math.PI / 180.0;   //PI()圆周率  
       var radLat2 = lat2 * Math.PI / 180.0;  
       var a = radLat1 - radLat2;  
       var b = (lng1 * Math.PI / 180.0) - (lng2 * Math.PI / 180.0);  
       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;  
        s = Math.round(s * 1000);  
       if (len_type --> 1)  
       {  
           s /= 1000;  
       }  
   return Math.round(s, decimal);  
},