[javascript] Function to calculate distance between two coordinates

Great-circle distance - From chord length

Here's an elegant solution applying the strategy design pattern; I hope it's readable enough.

TwoPointsDistanceCalculatorStrategy.js:

module.exports = () =>

class TwoPointsDistanceCalculatorStrategy {

    constructor() {}

    calculateDistance({ point1Coordinates, point2Coordinates }) {}
};

GreatCircleTwoPointsDistanceCalculatorStrategy.js:

module.exports = ({ TwoPointsDistanceCalculatorStrategy }) =>

class GreatCircleTwoPointsDistanceCalculatorStrategy extends TwoPointsDistanceCalculatorStrategy {

    constructor() {
        super();
    }

    /**
     * Following the algorithm documented here: 
     * https://en.wikipedia.org/wiki/Great-circle_distance#Computational_formulas
     * 
     * @param {object} inputs
     * @param {array} inputs.point1Coordinates
     * @param {array} inputs.point2Coordinates
     * 
     * @returns {decimal} distance in kelometers
     */
    calculateDistance({ point1Coordinates, point2Coordinates }) {

        const convertDegreesToRadians = require('../convert-degrees-to-radians');
        const EARTH_RADIUS = 6371;   // in kelometers

        const [lat1 = 0, lon1 = 0] = point1Coordinates;
        const [lat2 = 0, lon2 = 0] = point2Coordinates;

        const radianLat1 = convertDegreesToRadians({ degrees: lat1 });
        const radianLon1 = convertDegreesToRadians({ degrees: lon1 });
        const radianLat2 = convertDegreesToRadians({ degrees: lat2 });
        const radianLon2 = convertDegreesToRadians({ degrees: lon2 });

        const centralAngle = _computeCentralAngle({ 
            lat1: radianLat1, lon1: radianLon1, 
            lat2: radianLat2, lon2: radianLon2, 
        });

        const distance = EARTH_RADIUS * centralAngle;

        return distance;
    }
};


/**
 * 
 * @param {object} inputs
 * @param {decimal} inputs.lat1
 * @param {decimal} inputs.lon1
 * @param {decimal} inputs.lat2
 * @param {decimal} inputs.lon2
 * 
 * @returns {decimal} centralAngle
 */
function _computeCentralAngle({ lat1, lon1, lat2, lon2 }) {

    const chordLength = _computeChordLength({ lat1, lon1, lat2, lon2 });
    const centralAngle = 2 * Math.asin(chordLength / 2);

    return centralAngle;
}


/**
 * 
 * @param {object} inputs
 * @param {decimal} inputs.lat1
 * @param {decimal} inputs.lon1
 * @param {decimal} inputs.lat2
 * @param {decimal} inputs.lon2
 * 
 * @returns {decimal} chordLength
 */
function _computeChordLength({ lat1, lon1, lat2, lon2 }) {

    const { sin, cos, pow, sqrt } = Math;

    const ?X = cos(lat2) * cos(lon2) - cos(lat1) * cos(lon1);
    const ?Y = cos(lat2) * sin(lon2) - cos(lat1) * sin(lon1);
    const ?Z = sin(lat2) - sin(lat1);

    const ?XSquare = pow(?X, 2);
    const ?YSquare = pow(?Y, 2);
    const ?ZSquare = pow(?Z, 2);

    const chordLength = sqrt(?XSquare + ?YSquare + ?ZSquare);

    return chordLength;
}

convert-degrees-to-radians.js:

module.exports = function convertDegreesToRadians({ degrees }) {

    return degrees * Math.PI / 180;
};

This's following the Great-circle distance - From chord length, documented here.