javascript - 我想在选择下拉列表的最后一个选项时提交表单 选项是动态生成的

Question

例如，我在选择父项后添加字段，然后插入子项字段，我想在选择列表结束时提交表单或选择在最后一个子项上，如何在添加所有字段后提交，并且如果我没有子项选择然后提交

<script type="text/javascript">
var children = $H(<?php echo json_encode($tree['children']) ?>);

function showCat(obj, level) {
    var catId = obj.value;
    level += 1

    if ($('cat_container_' + level)) {
        $('cat_container_' + level).remove();


    }
    if (children.get(catId)) {
        var options = children.get(catId);
        var html = '<select id="cat_' + catId + '" onchange="showCat(this, ' + level + ')">';
        for (var i = 0; i < options.length; i++) {
            html += '<option value="' + options[i].entity_id + '">' + options[i].name + '</option>';
        }
        html += '</select>';
        html = '<div id="cat_container_' + level + '">' + html + '</div>';

        $('sub_cat').insert(html);
    }
}

Here is my form i m using onchange="this.form.submit()"

<form id="search_mini_form" action="<?php echo $catalogSearchHelper->getResultUrl() ?>" method="get">
<select id="first_cat" name="<?php echo $catalogSearchHelper->getQueryParamName() ?>" value="<?php echo $catalogSearchHelper->getEscapedQueryText() ?>"   onchange="showCat(this,2);this.form.submit()">
<?php foreach ($tree['first'] as $cat): ?>
    <option   value="<?php echo $cat->getId() ?>"><?php echo $cat->getName() ?> </option>
<?php endforeach ?>
</select>
<button type="submit" title="<?php echo $this->__('Search') ?>" class="button"><span><span><?php echo $this->__('Search') ?></span></span></button>

这段代码正在添加字段，但它在第一次选择时提交，我有一个选择树，我想在最后一次选择时提交

Answer 1

var strLastOptionSelected = $("select option:last-child").val();

$("select").change(function() {
  if ($(this).children("option:selected").val() === strLastOptionSelected) {
    alert("You have selected the last option");
    //Submit code
  }
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select>
  <option value="1">Option 1</option>
  <option value="2">Option 2</option>
  <option value="3">Option 3</option>
  <option value="4">Option 4</option>
</select>