Cross Browser Calculation of X & Y Position

gistfile1.js

function getPosition(e) {
  var posx = 0;
  var posy = 0;

  if (!e) var e = window.event;
  
  if (e.pageX || e.pageY) {
    posx = e.pageX;
    posy = e.pageY;
  }
  else if (e.clientX || e.clientY) {
    posx = e.clientX + document.body.scrollLeft
      + document.documentElement.scrollLeft;
    posy = e.clientY + document.body.scrollTop
      + document.documentElement.scrollTop;
  }

  return {
    x: posx,
    y: posy
  }
}

// usage

document.addEventListener( "click", function(e) {
  var x = getPosition(e).x;
  var y = getPosition(e).y;
  console.log("x pos: "+ x +" // y pos:"+ y);
});