Manhatan calc in js

manhatan.js

function distance(lat, long, lat1, long1, useManhatan) {

    var r = Math.sqrt;
    var o = Math.cos;
    var l = Math.sin;
    var p = Math.PI;
    var m = Math.round;

    var earthCurve = 6371;
    var manthatanConst = 1.309;
    
    var latresult = (lat1 - lat) * p / 180;
    var longr = (long1 - long) * p / 180;
    
    var distance = l(latresult / 2) * l(latresult / 2) + o(lat * p / 180) * o(lat1 * p / 180) * l(longr / 2) * l(longr / 2);
    var result = 2 * Math.atan2(r(distance), r(1 - distance));
    var c = earthCurve * result;
    
    return useManhatan ? (m(10 * (manthatanConst * c)) / 10).toFixed(1) : (m(10 * c) / 10).toFixed(1)
}