<header>
  <h2 class="title">getElementsByClassName() Method</h2>
  <p class="description">Allows accessing a list of elements with the same class name.</p>
</header>
<main>
  <div class="result">
    <p class="theme-text">Текст, який ми будемо стилізувати.</p>
    <p class="theme-text">Ще один рядок тексту для прикладу.</p>
    <button onclick="changeTheme('light')">Світла тема</button>
    <button onclick="changeTheme('dark')">Темна тема</button>
  </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);
}

.light-theme {
  color: black;
  background-color: white;
}

.dark-theme {
  color: white;
  background-color: #333;
}

button {
  margin: 5px;
  padding: 5px 10px;
  cursor: pointer;
}
function changeTheme(theme) {
  const elements = document.getElementsByClassName('theme-text');

  for (let i = 0; i < elements.length; i++) {
    if (theme === 'light') {
      elements[i].classList.remove('dark-theme');
      elements[i].classList.add('light-theme');
    } else if (theme === 'dark') {
      elements[i].classList.remove('light-theme');
      elements[i].classList.add('dark-theme');
    }
  }
}

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