@erexstudio/geo-span-measure/index.js

A simple npm package for calculating distance between two coordinates using the Haversine formula.

// index.js

const haversineDistance = (coord1, coord2, unit = "kilometers") => {
  if (!coord1 || !coord2) {
    return { error: "Both coordinates are required." };
  }
  if (
    !Array.isArray(coord1) ||
    coord1.length !== 2 ||
    !Array.isArray(coord2) ||
    coord2.length !== 2
  ) {
    return {
      error:
        "Invalid coordinates. Please provide arrays with latitude and longitude values for both coordinates.",
    };
  }

  const [lat1, lon1] = coord1;
  const [lat2, lon2] = coord2;

  if (
    typeof lat1 !== "number" ||
    typeof lon1 !== "number" ||
    typeof lat2 !== "number" ||
    typeof lon2 !== "number"
  ) {
    return {
      error:
        "Invalid coordinate values. Latitude and longitude should be numbers.",
    };
  }

  const earthRadius = {
    kilometers: 6357,
    miles: 3950,
    meters: 6371000,
  };

  if (!earthRadius[unit]) {
    return {
      error: `Invalid unit. Supported units are 'kilometers', 'miles', and 'meters'.`,
    };
  }

  const R = earthRadius[unit];
  const dLat = degToRad(lat2 - lat1);
  const dLon = degToRad(lon2 - lon1);

  const a =
    Math.sin(dLat / 2) * Math.sin(dLat / 2) +
    Math.cos(degToRad(lat1)) *
      Math.cos(degToRad(lat2)) *
      Math.sin(dLon / 2) *
      Math.sin(dLon / 2);

  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

  const distance = R * c;
  const formattedDistance = parseFloat(distance.toFixed(2));

  return formattedDistance;
};

const degToRad = (deg) => deg * (Math.PI / 180);

module.exports = haversineDistance;