Distance between two Points

What's the distance, in meters, between two points (given as latitude / longitude pairs)?

HTML

<div id="output"></div>

JavaScript

var path = [
    {name: 'Baltimore, MD, US', location: [39.28333333333333, -76.61666666666666]}
  
];

path.forEach(function(point, index, path) {
    var from = point;
    var to = path[(index + 1) % (path.length)];
    var meters = distanceBetweenLatLonPairs(from.location, to.location);
    var km = (meters / 1000).toFixed(2);
    var text = '<p>' + from.name + ' to ' + to.name + ' is '+ km + ' km';
    document.getElementById('output').innerHTML += text;
})

// Adopted from http://en.wikipedia.org/wiki/Haversine_formula
function distanceBetweenLatLonPairs(one, two) {

    // Earth's radius, in meters
    var r = 6371000;

    var lat1 = deg2rad(one[0]);
    var lon1 = deg2rad(one[1]);
    var lat2 = deg2rad(two[0]);
    var lon2 = deg2rad(two[1]);

    var deltaLat = lat2 - lat1;
    var deltaLon = lon2 - lon1;

    var h = haversin(deltaLat) + Math.cos(lat1) * Math.cos(lat2) * haversin(deltaLon);
    var d = (2 * r) * Math.asin(Math.sqrt(h));

    return d;
}

function haversin(rad) {
    return Math.pow(Math.sin(rad / 2), 2);
}

function deg2rad(deg) {
    return (deg / 180) * Math.PI;
}