deep-tree-clonenode.html | Explore in Territory

<!DOCTYPE html>
<script src="../resources/runner.js"></script>

<div id="source" style="display:none">
  <div></div>
</div>
<div id="destination" style="display:none"></div>

<script>
'use strict';

var sourceEl = document.getElementById('source').firstElementChild;
var destinationEl = document.getElementById('destination');

function buildTree(depth,parent) {
  while (depth--) {
    parent = parent.appendChild(document.createElement('span'));
  }
}

PerfTestRunner.measureRunsPerSecond({
  description: 'Measure the speed of cloning and appending a very deep tree',
  setup: () => {
    const treeDepth = 10000;
    if (!sourceEl.childNodes.length) {
      sourceEl.replaceChildren();
      buildTree(treeDepth, sourceEl);
      PerfTestRunner.assert_true(sourceEl.querySelectorAll('span').length === treeDepth,'Tree depth mismatch');
    }
    destinationEl.replaceChildren();
    PerfTestRunner.gc();
  },
  run: () => {
    destinationEl.appendChild(sourceEl.cloneNode(true));
  }
});
</script>

chromium/third_party/blink/perf_tests/dom/deep-tree-clonenode.html