HTML редактор

<!doctype html>
<html lang="ru">

<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Collapse</title>
  <link rel="stylesheet" href="/examples/libs/collapse/collapse.css">
  <style>
    *,
    *::before,
    *::after {
      box-sizing: border-box;
    }

body {
      margin: 0;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
      font-size: 1rem;
      font-weight: 400;
      line-height: 1.5;
      color: #212529;
      text-align: left;
      background-color: #fff;
    }

.container {
      max-width: 400px;
      margin-left: auto;
      margin-right: auto;
      padding: 20px;
    }

button {
      display: inline-block;
      font-weight: 400;
      font-size: inherit;
      line-height: 1.5;
      color: #212529;
      text-align: center;
      text-decoration: none;
      vertical-align: middle;
      cursor: pointer;
      -webkit-user-select: none;
      -moz-user-select: none;
      user-select: none;
      background-color: #eee;
      border: 1px solid #e0e0e0;
      padding: 0.375rem 0.75rem;
      font-size: 1rem;
      border-radius: 0.25rem;
      transition: color .15s ease-in-out, background-color .15s ease-in-out, border-color .15s ease-in-out, box-shadow .15s ease-in-out;
    }

button:hover {
      background-color: #e0e0e0;
      border-color: #bdbdbd;
    }

button {
      margin-bottom: 1rem;
    }

.collapse__body {
      word-wrap: break-word;
      background-color: #fff;
      background-clip: border-box;
      border: 5px solid rgba(139, 195, 74, .5);
      border-radius: 0.25rem;
      padding: 1rem;
    }
  </style>

</head>

<body>

<div class="container">
    <button id="toggle" type="button">SlideToggle</button>

<div class="collapse">
      <div class="collapse__body">
        <p>Lorem ipsum dolor sit amet consectetur, adipisicing elit. Aspernatur obcaecati animi corrupti, numquam
          explicabo maxime recusandae cupiditate amet velit sequi soluta nostrum vel consequuntur consectetur
          repellendus quia doloremque itaque eum!</p>
      </div>
    </div>
  </div>

const collapse = new ItcCollapse(document.querySelector('.collapse'));

document.querySelector('#toggle').onclick = () => {
      collapse.toggle();
    }
  </script>

</body>

</html>