HTML Markdown Previewer

I am trying to build an HTML markdown previewer, but I keep getting an uncaught error in my console even though my code seems to be okay.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Mardown Preview App</title>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" 
    integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" 
    crossorigin="anonymous" />
    <script src="https://kit.fontawesome.com/dfce6e7f73.js" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/marked/12.0.2/marked.min.js" 
    integrity="sha512-xeUh+KxNyTufZOje++oQHstlMQ8/rpyzPuM+gjMFYK3z5ILJGE7l2NvYL+XfliKURMpBIKKp1XoPN/qswlSMFA==" 
    crossorigin="anonymous" referrerpolicy="no-referrer"></script>
</head>
<body>
    <main class="container text-center">
        <div id="editor-area">
            <div>
                <h1>Editor</h1>
                <h1>
                    <div id="tog1">
                        <i class="fa-solid fa-maximize"></i>
                    </div>
                    <div id="tog2" style="display: none;">
                        <i class="fa-solid fa-minimize"></i>
                    </div>
                </h1>
            </div>
            <textarea id="editor" name="editor" id="" cols="80" rows="5"></textarea>
        </div>
        <div id="preview-area">
            <div>
                <h1>Preview</h1>
                <h1>
                    <div id="tog3">
                        <i class="fa-solid fa-maximize"></i>
                    </div>
                    <div id="tog4" style="display: none;">
                        <i class="fa-solid fa-minimize"></i>
                    </div>
                </h1>
            </div>
            <textarea id="preview" name="preview" id="" cols="80" rows="5" readonly disabled></textarea>
        </div>
    </main>
    <script>
        const editor = document.getElementById('editor');
        const preview = document.getElementById('preview');

        const updatePreview = () => {
            const editorInput = editor.value;
            const markdownHtml = marked(editorInput);
            preview.value = markdownHtml;

            console.log("Editor input:", editorInput);
            console.log("marked function:", marked);
            console.log("Preview updated");
        };

        editor.addEventListener('input', updatePreview);
    </script>
</body>
</html>

In the above code snippet I have inserted a markdown library in my <head> then called the marked() function in my updatePreview() function, yet I keep getting either "undefined" or "marked" is not a function in my console

Solution

marked is not a function but the marked API, which is why you're seeing a shed load of stuff being logged.

You wanted marked.parse() instead.

const editor = document.getElementById('editor');
const preview = document.getElementById('preview');

const updatePreview = () => {
  const editorInput = editor.value;
  const markdownHtml = marked.parse(editorInput);
  preview.value = markdownHtml;
};

editor.addEventListener('input', updatePreview);

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous" />
<script src="https://kit.fontawesome.com/dfce6e7f73.js" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/marked/12.0.2/marked.min.js" integrity="sha512-xeUh+KxNyTufZOje++oQHstlMQ8/rpyzPuM+gjMFYK3z5ILJGE7l2NvYL+XfliKURMpBIKKp1XoPN/qswlSMFA==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

<main class="container text-center">
  <div id="editor-area">
    <div>
      <h1>Editor</h1>
      <h1>
        <div id="tog1">
          <i class="fa-solid fa-maximize"></i>
        </div>
        <div id="tog2" style="display: none;">
          <i class="fa-solid fa-minimize"></i>
        </div>
      </h1>
    </div>
    <textarea id="editor" name="editor" id="" cols="80" rows="5"></textarea>
  </div>
  <div id="preview-area">
    <div>
      <h1>Preview</h1>
      <h1>
        <div id="tog3">
          <i class="fa-solid fa-maximize"></i>
        </div>
        <div id="tog4" style="display: none;">
          <i class="fa-solid fa-minimize"></i>
        </div>
      </h1>
    </div>
    <textarea id="preview" name="preview" id="" cols="80" rows="5" readonly disabled></textarea>
  </div>
</main>