/span></h2>
      <pre class="language-dart"><code class="language-dart">void insertAllBefore(Iterable&lt;Node&gt; newNodes, Node refChild) {
  if (newNodes is _ChildNodeListLazy) {
    _ChildNodeListLazy otherList = newNodes;
    if (identical(otherList._this, this)) {
      throw new ArgumentError(newNodes);
    }

    &#47;&#47; Optimized route for copying between nodes.
    for (var i = 0, len = otherList.length; i &lt; len; ++i) {
      this.insertBefore(otherList._this.firstChild, refChild);
    }
  }