js 多选 下拉框

<div class="multi-select">
  <div class="selected-options">Select options</div>
  <div class="options">
    <label><input type="checkbox" value="option1"> Option 1</label>
    <label><input type="checkbox" value="option2"> Option 2</label>
    <label><input type="checkbox" value="option3"> Option 3</label>
  </div>
</div>

.multi-select {
  position: relative;
  width: 200px;
}

.selected-options {
  border: 1px solid #ccc;
  padding: 8px;
  cursor: pointer;
}

.options {
  display: none;
  position: absolute;
  border: 1px solid #ccc;
  border-top: none;
  width: 100%;
  background-color: #fff;
}

.options label {
  display: block;
  padding: 8px;
  cursor: pointer;
}

.options label:hover {
  background-color: #f0f0f0;
}

document.querySelector('.selected-options').addEventListener('click', function() {
  document.querySelector('.options').style.display = document.querySelector('.options').style.display === 'block' ? 'none' : 'block';
});

document.querySelectorAll('.options input[type="checkbox"]').forEach(function(checkbox) {
  checkbox.addEventListener('change', function() {
    const selectedOptions = Array.from(document.querySelectorAll('.options input[type="checkbox"]:checked')).map(cb => cb.value);
    document.querySelector('.selected-options').textContent = selectedOptions.length ? selectedOptions.join(', ') : 'Select options';
  });
});