Javascript 使用jquery检测物化框架侧导航宽度

我试图检测materialize side nav元素是否打开，我的目标是在检测到side nav打开时运行一个函数下面的HTML标记来自materialize.css文档，其中side nav仅在屏幕处于移动大小时才会出现，所有操作都非常完美我只需要检测size nav是否打开

 <nav>
    <div class="nav-wrapper">
      <a href="#!" class="brand-logo">Logo</a>
      <a href="#" data-activates="mobile-demo" class="button-collapse"><i class="material-icons">menu</i></a>
      <ul class="right hide-on-med-and-down">
        <li><a href="sass.html">Sass</a></li>
        <li><a href="badges.html">Components</a></li>
        <li><a href="collapsible.html">Javascript</a></li>
        <li><a href="mobile.html">Mobile</a></li>
      </ul>
      <ul class="side-nav" id="mobile-demo">
        <li><a href="sass.html">Sass</a></li>
        <li><a href="badges.html">Components</a></li>
        <li><a href="collapsible.html">Javascript</a></li>
        <li><a href="mobile.html">Mobile</a></li>
      </ul>
    </div>
  </nav>

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但无法使其工作，任何建议将是伟大的提前感谢

如文档中提供的，您可以检测sidenav的打开和关闭，只需将其添加到选项中，如下所示

$('.button-collapse').sideNav({
      onOpen: function(el) { console.log('side nav is open');}, // A function to be called when sideNav is opened
      onClose: function(el) { console.log('side nav is close');}, // A function to be called when sideNav is closed
    }
  );

$('.button-collapse').sideNav({
      onOpen: function(el) { console.log('side nav is open');}, // A function to be called when sideNav is opened
      onClose: function(el) { console.log('side nav is close');}, // A function to be called when sideNav is closed
    }
  );