Javascript 三元运算符未按预期工作

Question

我正经历着最简单的逻辑不起作用的日子……

当我点击 link（id=show-additional-info）显示隐藏内容时，我试图切换图标的 class：

$(document).ready(function(){

  $("#show-additional-info").on('click',  function () {

    console.log('---------------');

    var iconToggle = $('#additional-info').attr("aria-expanded");        
    var active_icon = iconToggle 
            ? 'fa fa-chevron-circle-right' 
            : 'fa fa-chevron-circle-down';

    $('#icon-toggle').attr("class", active_icon);

    // show state of trigger event, ternary operator, and affected element class
    console.log('additional-info.aria-expanded: ' + iconToggle);
    console.log('active_icon: ' + active_icon);
    console.log('icon-toggle.class: ' + $('#icon-toggle').attr("class"));
  });
});

控制台日志显示第一个状态为未定义，这是预期的，应该是假的。通过反复点击，我看到 aria-expanded 属性在 true 和 false 之间切换状态。但是三元运算符没有像我期望的那样赋值：

---------------
additional-info.aria-expanded: undefined
active_icon: fa fa-chevron-circle-down     // <-- correctly assigns state. 
icon-toggle.class: fa fa-chevron-circle-down
---------------
additional-info.aria-expanded: true
active_icon: fa fa-chevron-circle-right    // <-- correctly changes state.
icon-toggle.class: fa fa-chevron-circle-right
---------------
additional-info.aria-expanded: false
active_icon: fa fa-chevron-circle-right    // <-- should be circle down!
icon-toggle.class: fa fa-chevron-circle-right
---------------
additional-info.aria-expanded: true
active_icon: fa fa-chevron-circle-right
icon-toggle.class: fa fa-chevron-circle-right
---------------
additional-info.aria-expanded: false
active_icon: fa fa-chevron-circle-right    // <-- should be circle down!
icon-toggle.class: fa fa-chevron-circle-right

html 部分按预期工作，似乎没有涉及这种意外行为，但为了完整起见，这里是：

  <i id="icon-toggle" class="fa fa-chevron-circle-right" aria-hidden="true"></i>&nbsp;<a id="show-additional-info" href="#additional-info" data-toggle="collapse">Additional Batch Info</a><br><br>
  <div>
    <ul id="additional-info" class="list-unstyled collapse">

    <!-- stuff... --->

    </ul>
  </div>

对于我来说，我看不出我在使用三元运算符时做错了什么。另一组眼睛将不胜感激！

Answer 1

您是否考虑过使用 toggleClass() 方法使它变得更简单？

$(document).ready(function(){
   $("#show-additional-info").on('click',  function () {
      $("#icon-toggle").toggleClass("fa-chevron-circle-right fa-chevron-circle-down")
  });
});

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<i id="icon-toggle" class="fa fa-chevron-circle-right" aria-hidden="true"></i>&nbsp;
<a id="show-additional-info" href="#additional-info" data-toggle="collapse">Additional Batch Info</a>
<br><br>
  <div>
    <ul id="additional-info" class="list-unstyled collapse">

    <!-- stuff... --->

    </ul>
  </div>

Answer 2

我发布问题后不久，答案打动了我：

'false' == true

我以为我在测试一个布尔值，但它实际上是一个字符串。我将代码更改为

var active_icon = iconToggle == 'true'
        ? 'fa fa-chevron-circle-right' 
        : 'fa fa-chevron-circle-down';

它按预期工作。

然而，更好的答案是不要重新发明轮子，正如公认的答案所示：

$("#icon-toggle").toggleClass("fa-chevron-circle-right fa-chevron-circle-down")

Javascript 三元运算符未按预期工作

Javascript ternary operator not working as expected

javascript

jquery

ternary-operator