Calculate Distance Between Two Coordinates in JavaScript (Haversine Formula)

The Haversine Formula

The most popular way of calculating the distance between two points on a sphere is using the Haversine equation. If you have the coordinates (longitude and latitude) of the starting and destination locations, you can use this equation to calculate the distance.

Here's how to calculate the distance in kilometers between two locations using JavaScript and the Geolocation API.

By default, coordinates obtained from the Geolocation API are given in degrees. We need them in radians for the formula. Here's our conversion function:

// Convert from degrees to radians
function degreesToRadians(degrees) {
  var radians = (degrees * Math.PI) / 180;
  return radians;
}

Here's the function to calculate the distance using coordinates (longitude and latitude):

// Function takes two objects, that contain coordinates to a starting and destination location.
function calcDistance(startingCoords, destinationCoords) {
  let startingLat = degreesToRadians(startCoords.latitude);
  let startingLong = degreesToRadians(startCoords.longitude);
  let destinationLat = degreesToRadians(destCoords.latitude);
  let destinationLong = degreesToRadians(destCoords.longitude);

  // Radius of the Earth in kilometers
  let radius = 6571;

  // Haversine equation
  let distanceInKilometers =
    Math.acos(
      Math.sin(startingLat) * Math.sin(destinationLat) +
        Math.cos(startingLat) *
          Math.cos(destinationLat) *
          Math.cos(startingLong - destinationLong)
    ) * radius;

  return distanceInKilometers;
}

Now, you can call the calcDistance function and pass it any two coordinates. For example:

let sCoords = {
latitude: 58.39343;
longitude: -259.2627;
}

let dCoords = {
latitude: 43.8394;
longitude: -129.3984;
}
let dist = calcDistance(sCoords, dCoords)