Mini program example: How to calculate the distance between two points based on longitude and latitude (code)

//计算两点位置距离
  getDistance: function (lat1, lng1, lat2, lng2) {
    lat1 = lat1 || 0;
    lng1 = lng1 || 0;
    lat2 = lat2 || 0;
    lng2 = lng2 || 0;    
    var rad1 = lat1 * Math.PI / 180.0;    
    var rad2 = lat2 * Math.PI / 180.0;    
    var a = rad1 - rad2;    
    var b = lng1 * Math.PI / 180.0 - lng2 * Math.PI / 180.0;    
    var r = 6378137;  //地球半径
    var distance = r * 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2) + Math.cos(rad1) * Math.cos(rad2) * Math.pow(Math.sin(b / 2), 2)));    
    /*
    if (distance > 1000){
      distance = Math.round(distance / 1000);
    }*/

    return distance;
  }