documentOffsetTop vs offset().top

JavaScript performance comparison

Revision 2 of this test case created by Renan

Preparation code

<div id="static" class="offset">
  0
</div>
<div id="static2" class="offset">
  0
</div>
<div id="static-wrapped-static">
  <br />
  <div class="offset">
    0
  </div>
</div>
<div id="absolute" class="offset">
  0
</div>
<div id="relative" class="offset">
  0
</div>
<div id="fixed-side" class="offset">
  0
</div>
<div id="fixed-top" class="offset">
  0
</div>
<div id="fixed-bottom" class="offset">
  0
</div>
<div style="position: relative;">
  <div id="relative-wrapped-absolute">
    <div class="offset">
      0
    </div>
  </div>
</div>
<style>
  body {padding-left: 12px;} #absolute { top: 100px; position: absolute; } #relative
  { top: 150px; position: relative; } #fixed-side { right: 0; position: fixed; } #fixed-top
  { left: 50%; position: fixed; top: 0; } #fixed-bottom { left: 50%; position: fixed;
  bottom: 0; } #relative-wrapped-absolute { top: 8px; position: relative; } #relative-wrapped-absolute
  div { position: absolute; top: 20px; } .offset { border: 1px solid black; } #grid
  { height: 100%; left: 0; position: absolute; top: 1px; width: 100%; z-index: -1;
  } .grid-line { border-bottom: 1px solid lightgray; font-size: 8px; height: 9px; line-height:
  20px; }
</style>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js">
</script>
<script>
Benchmark.prototype.setup = function() {
    Element.prototype.documentOffsetTop = function() {
      return this.offsetTop + (this.offsetParent ? this.offsetParent.documentOffsetTop : 0);
    };
};
</script>

Preparation code output

0
0

0
0
0
0
0
0
0

Test runner

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Testing in unknown unknown
Test Ops/sec
documentOffsetTop
for (i = 0; i < 150; i++) {
  var offset = document.getElementById('absolute');
  offset.textContent = 'absolute: ' + offset.documentOffsetTop();

  offset = document.getElementById('static');
  offset.textContent = 'static: ' + offset.documentOffsetTop();

  offset = document.getElementById('static2');
  offset.textContent = 'static: ' + offset.documentOffsetTop();

  offset = document.getElementById('relative');
  offset.textContent = 'relative: ' + offset.documentOffsetTop();

  offset = document.getElementById('fixed-side');
  offset.textContent = 'fixed/absolute (side): ' + offset.documentOffsetTop();

  offset = document.getElementById('fixed-top');
  offset.textContent = 'fixed/absolute (top): ' + offset.documentOffsetTop();

  offset = document.getElementById('fixed-bottom');
  offset.textContent = 'fixed/absolute (bottom): ' + offset.documentOffsetTop();

  offset = document.querySelectorAll('#relative-wrapped-absolute div')[0];
  offset.textContent = 'absolute/relative/static (absolute/relative wrapped): ' + offset.documentOffsetTop();

  offset = document.querySelectorAll('#static-wrapped-static div')[0];
  offset.textContent = 'static (static wrapped): ' + offset.documentOffsetTop();
}
pending…
offset().top
for (i = 0; i < 150; i++) {
  var offset = document.getElementById('absolute');
  offset.textContent = 'absolute: ' + $(offset).offset().top;

  offset = document.getElementById('static');
  offset.textContent = 'static: ' + $(offset).offset().top;

  offset = document.getElementById('static2');
  offset.textContent = 'static: ' + $(offset).offset().top;

  offset = document.getElementById('relative');
  offset.textContent = 'relative: ' + $(offset).offset().top;

  offset = document.getElementById('fixed-side');
  offset.textContent = 'fixed/absolute (side): ' + $(offset).offset().top;

  offset = document.getElementById('fixed-top');
  offset.textContent = 'fixed/absolute (top): ' + $(offset).offset().top;

  offset = document.getElementById('fixed-bottom');
  offset.textContent = 'fixed/absolute (bottom): ' + $(offset).offset().top;

  offset = document.querySelectorAll('#relative-wrapped-absolute div')[0];
  offset.textContent = 'absolute/relative/static (absolute/relative wrapped): ' + $(offset).offset().top;

  offset = document.querySelectorAll('#static-wrapped-static div')[0];
  offset.textContent = 'static (static wrapped): ' + $(offset).offset().top;
}
pending…

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1 comment

cow commented :

Shouldn't this

return this.offsetTop + (this.offsetParent ? this.offsetParent.documentOffsetTop : 0);

be

return this.offsetTop + (this.offsetParent ? this.offsetParent.documentOffsetTop() : 0);

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