A conversion from Geographic (Latitude & Longitude) to Web Mercator (X & Y)

LatLong2Merc.js

_latLong2Merc = (_lat, _lon) => {
  /*
  _lat => Latitude in decimal degree (Number)
  _lon => Longitude in decimal degree (Number)
  */
  var r_major = 6378137.000
  var lon_rad = (_lon / 180.0 * Math.PI)
  var x = r_major * lon_rad
  var scale = x / _lon
  var y = 180.0 / Math.PI * Math.log(Math.tan(Math.PI / 4.0 + _lat * (Math.PI / 180.0) / 2.0)) * scale
  return ({ x, y });
}

Results were tested by PostGIS ST_Transform function.