Question

在我提出这个问题之前，如果有人不想给我答案，请不要将这篇帖子分配为已解决，因为在这种情况下，该解决方案都无法帮助我。

这是我的代码：

// Collapse Navbar
var navbarCollapse = function() {
  if ($("#mainNav").offset().top > 100) {
    $("#mainNav").addClass("navbar-shrink");
  } else {
    $("#mainNav").removeClass("navbar-shrink");
  }
};

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js"></script>
<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" rel="stylesheet"/>

<nav class="navbar navbar-expand-lg navbar-light fixed-top" id="mainNav">
  <div class="container">
    <a class="navbar-brand js-scroll-trigger" href="#page-top">Start Bootstrap</a>
    <button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarResponsive" aria-controls="navbarResponsive" aria-expanded="false" aria-label="Toggle navigation">
          <span class="navbar-toggler-icon"></span>
        </button>
    <div class="collapse navbar-collapse" id="navbarResponsive">
      <ul class="navbar-nav ml-auto">
        <li class="nav-item">
          <a class="nav-link js-scroll-trigger" href="#about">About</a>
        </li>
        <li class="nav-item">
          <a class="nav-link js-scroll-trigger" href="#services">Services</a>
        </li>
        <li class="nav-item">
          <a class="nav-link js-scroll-trigger" href="#portfolio">Portfolio</a>
        </li>
        <li class="nav-item">
          <a class="nav-link js-scroll-trigger" href="#contact">Contact</a>
        </li>
      </ul>
    </div>
  </div>
</nav>

Answer 1

我可以通过分隔声明和方法调用来解决此问题：

var navbarCollapse = function() {
  var mainNav = $("#mainNav");
  if (mainNav.offset().top > 100) {
    mainNav.addClass("navbar-shrink");
  } else {
    mainNav.removeClass("navbar-shrink");
  }
};

错误：“未捕获的TypeError：无法读取未定义的属性'top'”

1 个答案: