function distance()

in region-optimizer.js [23:37]

• 12 lines of code
• 1 McCabe index (conditional complexity)

function distance(destination, origin) {
    // Thanks https://www.movable-type.co.uk/scripts/latlong.html
    const R = 6371e3; // metres
    const φ1 = origin.latitude * Math.PI / 180; // φ, λ in radians
    const φ2 = destination.latitude * Math.PI / 180;
    const Δφ = (destination.latitude - origin.latitude) * Math.PI / 180;
    const Δλ = (destination.longitude - origin.longitude) * Math.PI / 180;

    const a = Math.sin(Δφ / 2) * Math.sin(Δφ / 2) +
        Math.cos(φ1) * Math.cos(φ2) *
        Math.sin(Δλ / 2) * Math.sin(Δλ / 2);
    const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

    return R * c; // in metres
}