nested-insertion-point-1.html

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<!DOCTYPE HTML>

<html>

<head>

  <script>

    function tweak() {

      // div with style "border: 10px solid green"

      var outerShadow = document.createElement("div");

      outerShadow.style.border = "10px solid green";

      var outerInsertionPoint = document.createElement("slot");

      outerShadow.appendChild(outerInsertionPoint);

      // div with style "border: 10px solid orange"

      var innerShadow = document.createElement("div");

      innerShadow.style.border = "10px solid orange";

      var slot = document.createElement("slot");

      innerShadow.appendChild(slot);

      outerShadow.attachShadow({mode: 'open'}).appendChild(innerShadow);

      var shadowRoot =

        document.getElementById('outer').attachShadow({mode: 'open'});

      shadowRoot.appendChild(outerShadow);

  </script>

</head>

<body onload="tweak()">

<div id="outer">Hello</div>

</body>

</html>