时间三级联动js

<select id="year"></select>
<select id="month"></select>
<select id="day"></select>

<script>
const yearSelect = document.getElementById('year');
const monthSelect = document.getElementById('month');
const daySelect = document.getElementById('day');

// 初始化年份选项
for (let year = 1900; year <= 2100; year++) {
    const option = document.createElement('option');
    option.value = year;
    option.text = year;
    yearSelect.appendChild(option);
}

// 根据年份和月份更新日期选项
function updateDays() {
    const year = parseInt(yearSelect.value);
    const month = parseInt(monthSelect.value);
    const daysInMonth = new Date(year, month + 1, 0).getDate(); // JavaScript中月份从0开始计数
    
    daySelect.innerHTML = ''; // 清空日期选项
    for (let day = 1; day <= daysInMonth; day++) {
        const option = document.createElement('option');
        option.value = day;
        option.text = day;
        daySelect.appendChild(option);
    }
}

// 初始化月份选项并绑定事件
for (let month = 1; month <= 12; month++) {
    const option = document.createElement('option');
    option.value = month;
    option.text = month;
    monthSelect.appendChild(option);
}
monthSelect.addEventListener('change', updateDays);

// 绑定年份选择事件（考虑闰年和平年）
yearSelect.addEventListener('change', updateDays);

// 初始化日期选项
updateDays();
</script>