[解決済み] TypeError: document.getElementbyId is not a function [closed].

function showSource() {
  var content = document.getElementbyId("edit").innerHTML
  content.replace(/</g, '&lt;');
  content.replace(/>/, '&gt: ');
  prompt("Your Code:", content);

}

function createLink() {
  var url = prompt("Enter URL:", "http://");
  if (url)
    document.execCommand("createlink", false, url);
}

<h1>Native Rich Text</h1>
<p>No textboxes here, that's a &lt;div&gt; element!</p>
<div>
  <input type="button" value="Bold" onclick="document.execCommand('bold', false, null);">
  <input type="button" value="Italic" onclick="document.execCommand('italic', false, null);">
  <input type="button" value="Underline" onclick="document.execCommand('underline', false, null);">
  <input type="button" value="Add Link" onclick="createLink();">
  <input type="button" value="Show Source" onclick="showSource();">
</div>
<div id="edit" style="border:solid black; height: 300px; width: 400px;" contenteditable="true">
  Hello!
</div>