jquery - 更改所有下拉列表时应用 CSS Jquery

Question

当所有下拉列表都更改时，我必须应用一些 CSS。请帮我解决一下这个。

$("select").change(function() {
  alert('test');
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select name="company1" class="dropdown">
  <option value="1">Group 1</option>
  <option value="2">Group 2</option>
</select>
<select name="company2" class="dropdown">
  <option value="1">Group 1</option>
  <option value="2">Group 2</option>
</select>
<select name="company3" class="dropdown">
  <option value="1">Group 1</option>
  <option value="2">Group 2</option>
</select>

标签： jquery

Answer 1

var cnt1=0,cnt2=0,cnt3=0;
$(".one").change(function(){
    cnt1=1;
    if((cnt1==1) && (cnt2==1) && (cnt3==1)){
        alert('test');
    }
});
$(".two").change(function(){
    cnt2=1;
    if((cnt1==1) && (cnt2==1) && (cnt3==1)){
        alert('test');
    }
});
$(".three").change(function(){
    cnt3=1;
    if((cnt1==1) && (cnt2==1) && (cnt3==1)){
        alert('test');
    }
});
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
    <select name="company1" class="dropdown one">
        <option value="1">Group 1</option>
        <option value="2">Group 2</option>
    </select>
    <select name="company2" class="dropdown two">
        <option value="1">Group 1</option>
        <option value="2">Group 2</option>
    </select>
    <select name="company3" class="dropdown three">
        <option value="1">Group 1</option>
        <option value="2">Group 2</option>
    </select>