如何要求至少选中一个复选框才能让用户提交表单？

<script>
    function validateForm() {
        var checkboxes = document.getElementsByName('checkbox');
        var checked = false;
        for (var i = 0; i < checkboxes.length; i++) {
            if (checkboxes[i].checked) {
                checked = true;
                break;
            }
        }
        if (!checked) {
            alert('请至少选择一个复选框');
            return false;
        }
    }
</script>

<form onsubmit="return validateForm()">
    <input type="checkbox" name="checkbox" value="option1">选项1
    <input type="checkbox" name="checkbox" value="option2">选项2
    <input type="checkbox" name="checkbox" value="option3">选项3
    <input type="submit" value="提交">
</form>

<form>
    <input type="checkbox" name="checkbox" value="option1" required>选项1
    <input type="checkbox" name="checkbox" value="option2" required>选项2
    <input type="checkbox" name="checkbox" value="option3" required>选项3
    <input type="submit" value="提交">
</form>