<header>
  <h2 class="title">element.style.columnRule</h2>
  <p class="description">Встановлює стиль, товщину та колір лінії між колонками у багатоколонковому макеті.</p>
</header>
<main>
  <div class="result">
    <div id="content">
      Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus imperdiet, nulla et dictum interdum, nisi lorem egestas odio, vitae scelerisque enim ligula venenatis dolor. Maecenas nisl est, ultrices nec congue eget, auctor vitae massa. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus imperdiet, nulla et dictum interdum, nisi lorem egestas odio, vitae scelerisque enim ligula venenatis dolor. Maecenas nisl est, ultrices nec congue eget, auctor vitae massa.
    </div>
    <div class="controls">
      <label for="thickness">Товщина (px):</label>
      <input type="number" id="thickness" value="2" min="1" max="10"><br>
      <label for="style">Стиль лінії:</label>
      <select id="style">
        <option value="solid">Solid</option>
        <option value="dashed">Dashed</option>
        <option value="dotted">Dotted</option>
      </select><br>
      <label for="color">Колір:</label>
      <input type="color" id="color" value="#ff0000"><br>
      <button id="apply">Застосувати</button>
    </div>
  </div>
</main>
body {
  font-size: 16px;
  line-height: 1.5;
  font-family: monospace;
}

header {
  background-color: #f1f1f1;
  margin-bottom: 25px;
  padding: 15px;
  -webkit-box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
  -moz-box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
  box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
}

header h2.title {
  padding-bottom: 15px;
  border-bottom: 1px solid #999;
}

header p.description {
  font-style: italic;
  color: #222;
}

.result {
  background-color: #f8f8f8;
  padding: 15px;
  -webkit-box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
  -moz-box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
  box-shadow: 0px 0px 3px 0px rgba(118, 118, 118, 1);
}

#content {
  column-count: 3;
  column-gap: 20px;
  column-rule: 2px solid red;
  margin-bottom: 15px;
}

.controls label, .controls input, .controls select, .controls button {
  display: block;
  margin-bottom: 10px;
}
document.getElementById('apply').addEventListener('click', function() {
  let thickness = document.getElementById('thickness').value + 'px';
  let style = document.getElementById('style').value;
  let color = document.getElementById('color').value;
  let columnRule = `${thickness} ${style} ${color}`;

  let content = document.getElementById('content');
  content.style.columnRule = columnRule;
});

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