getBoundingClientRect() Method

요소의 left, top, width, height 값을 반환한다. 

function myFunction() {

  var div = document.getElementById("myDiv");

  var rect = div.getBoundingClientRect();

  x = rect.left;

  y = rect.top;

  w = rect.width;

  h = rect.height;

  alert ("Left: " + x + ", Top: " + y + ", Width: " + w + ", Height: " + h);

}