js 上移 下移

function moveUp(arr, index) {
    if (index <= 0) return arr;
    [arr[index], arr[index - 1]] = [arr[index - 1], arr[index]];
    return arr;
}

function moveDown(arr, index) {
    if (index >= arr.length - 1) return arr;
    [arr[index], arr[index + 1]] = [arr[index + 1], arr[index]];
    return arr;
}

// 示例
let arr = [1, 2, 3, 4, 5];
arr = moveUp(arr, 2); // [1, 3, 2, 4, 5]
arr = moveDown(arr, 1); // [1, 2, 3, 4, 5]

<ul id="list">
    <li>Item 1</li>
    <li>Item 2</li>
    <li>Item 3</li>
    <li>Item 4</li>
    <li>Item 5</li>
</ul>

<button onclick="moveUp('item2')">Move Item 2 Up</button>
<button onclick="moveDown('item2')">Move Item 2 Down</button>

<script>
function moveUp(elementId) {
    let element = document.getElementById(elementId);
    let prevElement = element.previousElementSibling;
    if (prevElement) {
        element.parentNode.insertBefore(element, prevElement);
    }
}

function moveDown(elementId) {
    let element = document.getElementById(elementId);
    let nextElement = element.nextElementSibling;
    if (nextElement) {
        element.parentNode.insertBefore(nextElement, element);
    }
}
</script>