function getDistance(lat1, lon1, lat2, lon2) {
    // pastikan semuanya number
    lat1 = parseFloat(lat1);
    lon1 = parseFloat(lon1);
    lat2 = parseFloat(lat2);
    lon2 = parseFloat(lon2);
  
    const R = 6371000; // radius bumi dalam meter
    const toRad = Math.PI / 180;
    
    const dLat = (lat2 - lat1) * toRad;
    const dLon = (lon2 - lon1) * toRad;
  
    const a =
      Math.sin(dLat / 2) * Math.sin(dLat / 2) +
      Math.cos(lat1 * toRad) *
      Math.cos(lat2 * toRad) *
      Math.sin(dLon / 2) * Math.sin(dLon / 2);
  
    const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    const distance = R * c;
  
    return distance;
  }
  
  module.exports = { getDistance };