Calculate distance between two points in google maps V3

Question

How do you calculate the distance between two markers in Google maps V3? (Similar to the distanceFrom function inV2.)

Thanks..

Answer 1

  /**
   * Calculates the haversine distance between point A, and B.
   * @param {number[]} latlngA [lat, lng] point A
   * @param {number[]} latlngB [lat, lng] point B
   * @param {boolean} isMiles If we are using miles, else km.
   */
  function haversineDistance(latlngA, latlngB, isMiles) {
    const squared = x => x * x;
    const toRad = x => (x * Math.PI) / 180;
    const R = 6371; // Earth’s mean radius in km

    const dLat = toRad(latlngB[0] - latlngA[0]);
    const dLon = toRad(latlngB[1] - latlngA[1]);

    const dLatSin = squared(Math.sin(dLat / 2));
    const dLonSin = squared(Math.sin(dLon / 2));

    const a = dLatSin +
              (Math.cos(toRad(latlngA[0])) * Math.cos(toRad(latlngB[0])) * dLonSin);
    const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    let distance = R * c;

    if (isMiles) distance /= 1.609344;

    return distance;
  }

I found a version online which is 80% right but plugged in the wrong parameter and is inconsistent in using the inputs, this version fixed that completely