Get distance by Latitude & Longitude KM/Meters/Miles

Distances.js

var Distance = (function () {

    var toRad = function (num) {
        return num * Math.PI / 180
    }

    return function Distance(start, end, options) {
        options = options || {}

        var radii = {
            km: 6371,
            mile: 3960,
            meter: 6371000,
            nmi: 3440
        }

        var R = options.unit in radii
            ? radii[options.unit]
            : radii.km

        var dLat = toRad(end.latitude - start.latitude)
        var dLon = toRad(end.longitude - start.longitude)
        var lat1 = toRad(start.latitude)
        var lat2 = toRad(end.latitude)

        var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
            Math.sin(dLon / 2) * Math.sin(dLon / 2) * Math.cos(lat1) * Math.cos(lat2)
        var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a))

        if (options.threshold) {
            return options.threshold > (R * c)
        }

        return R * c
    }

})()

export { Distance }