convert rad to tiles js

gistfile1.txt

Math.radians = function(degrees) {
  return degrees * Math.PI / 180;
};

var zoom = 8;
var lon = 5.2206592;
var lat = 49.1154095; 
var xtile = Math.floor(((lon+180)/360) * Math.pow(2,zoom));
var ytile = Math.floor((1- Math.log(Math.atan(Math.radians(lat)) + 1 / Math.cos(Math.radians(lat))) / Math.PI) / 2 * Math.pow(2,zoom));

console.log('xtile: ' + xtile);
console.log('ytile: ' + ytile);