src/textarea/example.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Textarea</title>
    <style>
      body {
        font: normal 16px/1.5 Ubuntu, sans-serif;
        margin: 100px;
      }

      .form-group {
        margin-bottom: 1rem;
      }

      label {
        display: block;
        margin-bottom: 0.5rem;
      }

      dice-textarea {
        width: 100%;
      }

      input {
        padding: 0.375rem 0.75rem;
      }

      dice-textarea::part(wrapper),
      dice-textarea::part(textarea) {
        max-height: 100px;
      }

      dice-textarea::part(wrapper) {
        --padding: 0.375rem 0.75rem;
      }

      input,
      dice-textarea::part(textarea) {
        display: block;
        width: 100%;
        font-size: 1rem;
        font-weight: 400;
        line-height: 1.5;
        color: #212529;
        border: 1px solid #ced4da;
        appearance: none;
        border-radius: 0.25rem;
        transition: border-color 0.15s ease-in-out, box-shadow 0.15s ease-in-out;
      }

      input:focus,
      dice-textarea::part(textarea):focus-within {
        border-color: #86b7fe;
        outline: 0;
        box-shadow: 0 0 0 0.25rem rgb(13 110 253 / 25%);
      }

      button {
        --background-color: #6c757d;
        --border-color: var(--background-color);

        display: flex;
        align-items: center;
        cursor: pointer;
        color: #fff;
        font: inherit;
        background-color: var(--background-color);
        border: 1px solid var(--border-color);
        padding: 0.375rem 0.75rem;
        border-radius: 0.25rem;
        transition: color 0.15s ease-in-out, background-color 0.15s ease-in-out, border-color 0.15s ease-in-out,
          box-shadow 0.15s ease-in-out;
      }

      button:hover,
      button:focus {
        --background-color: #5c636a;
      }
    </style>
  </head>
  <body>
    <form>
      <div class="form-group">
        <label for="name">Your name:</label>
        <input type="text" name="name" id="name" />
      </div>

      <div class="form-group">
        <label for="bio">Your biography:</label>
        <dice-textarea name="bio" id="bio" placeholder="Start writing..." required pattern="[0-9]{3}"></dice-textarea>
      </div>

      <button type="submit">Submit</button>
    </form>
    <p>Design by Bootstrap 5.</p>

    <script src="textarea.js" defer></script>
    <script>
      document.querySelector('form').addEventListener('submit', (evt) => {
        evt.preventDefault();

        console.log(evt.target[1].value);
      });

      document.querySelector('dice-textarea').addEventListener('change', (evt) => {
        console.log(evt.target.value);
      });
    </script>
  </body>
</html>