Optimised retrieve offset in vanilla js

gistfile1.js

// FROM http://jsperf.com/test-offset-jquery-vs-vanilla
function offset(elt) {
var rect = elt.getBoundingClientRect(), bodyElt = document.body;

return {
  top: rect.top + bodyElt .scrollTop,
  left: rect.left + bodyElt .scrollLeft
}
}
var offsetElt = offset(document.getElementById('element'));
offsetElt.top;
offsetElt.left;