merc.js

function merc(lat, lon) {
    let r_major = 6378137.000,
    x = r_major * toRadians(lon),
    scale = x/lon,
    y = 180.0/Math.PI * Math.log(Math.tan(Math.PI/4.0 + lat * (Math.PI/180.0)/2.0)) * scale;
    return (x, y)
}

function toRadians (angle) {
  return angle * (Math.PI / 180);
}