<!doctype html>
<html>
<head>
<meta charset="utf-8">
<script>
document.addEventListener("DOMContentLoaded", () => {
  const output = document.querySelector("output");
  const table = document.querySelector("table");
  table.addEventListener("DOMSubtreeModified", () => {
    document.execCommand("bold");
    document.execCommand("hiliteColor", false, "white");
    output.appendChild(table);
    document.execCommand("forwardDelete");
    table.setAttribute("onwebkitsourceclose", "foo()");
    document.execCommand("insertText", false, "a");
  });
  document.execCommand("selectAll");
  table.insertRow();
});
</script>
</head>
<body>
<canvas contenteditable>
<output>
<table tabindex="0" autofocus></table>
</output>
</canvas>
</body>
</html>
