Edit in JSFiddle

function getRectangle(rec) {
  var rects = rec.getClientRects();
  var bundingrect = rec.getBoundingClientRect();
  console.log(rects);
  console.log(bundingrect);
};
(function() {
  var classes = document.getElementsByClassName('seq');
  for (var i = 0; i < classes.length; i++) {
    getRectangle(classes[i]); //
  }
})()

<div class="target1 seq"></div>
<div class="target2 seq"></div>
<div class="target3 seq"></div>
<div class="target4 seq"></div>

.seq {
  width: 50px;
}

.target1 {
  background: #3e3e3e;
}