除非导航栏已经堆叠，否则粘性导航栏中的内部链接不会链接到正确的位置

Question

我正在用纯HTML和CSS编写基于粘性导航栏的导航系统。我在导航栏上有一些内部链接，这些链接指向页面的相应部分。

为防止内容跳转到页面顶部并被导航栏部分隐藏，我在内容顶部添加了一个适当高度的简单div，然后跳转到该div。

我已经在Codepen上创建了一个示例：https://codepen.io/anon/pen/yqvwNX

代码如下：

window.onscroll = function() {
  myFunction()
};

var navbar = document.getElementById("navbar");
var sticky = navbar.offsetTop;

function myFunction() {
  if (window.pageYOffset >= sticky) {
    navbar.classList.add("sticky")
  } else {
    navbar.classList.remove("sticky");
  }
}

body {
  margin: 0;
  font-size: 28px;
}

.header {
  background-color: #f1f1f1;
  padding: 30px;
  text-align: center;
}

#navbar {
  overflow: hidden;
  background-color: #333;
}

#navbar a {
  float: left;
  display: block;
  color: #f2f2f2;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
  font-size: 17px;
}

#navbar a:hover {
  background-color: #ddd;
  color: black;
}

#navbar a.active {
  background-color: #4CAF50;
  color: white;
}

.content {
  padding: 16px;
}

.sticky {
  position: fixed;
  top: 0;
  width: 100%;
}

.sticky+.content {
  padding-top: 60px;
}

<div class="header">
  <h2>Scroll Down</h2>
  <p>Scroll down to see the sticky effect.</p>
</div>

<div id="navbar">
  <a class="active" href="javascript:void(0)">Home</a>
  <a href="#goto">Goto h4</a>
</div>

<div class="content">
  <h3>Sticky Navigation Example</h3>
  <p>The navbar will stick to the top when you reach its scroll position.</p>
  <p>Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint
    efficiantur his ad. Eum no molestiae voluptatibus.</p>
  <p>Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint
    efficiantur his ad. Eum no molestiae voluptatibus.</p>
  <div id="goto" style="height:30px;"></div>
  <h4>Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint
    efficiantur his ad. Eum no molestiae voluptatibus.</h4>
  <p>Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint
    efficiantur his ad. Eum no molestiae voluptatibus.</p>
  <p>Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint
    efficiantur his ad. Eum no molestiae voluptatibus.</p>
  <p>Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint
    efficiantur his ad. Eum no molestiae voluptatibus.</p>
  <p>Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint
    efficiantur his ad. Eum no molestiae voluptatibus.</p>
</div>

问题：

情况1：在导航栏停靠之前，您单击导航栏按钮以转到粗体（h3标签）段落。

情况2：在导航栏停靠后，您点击导航栏按钮以转到粗体（h3标签）段落。

页面上内容的最终位置不同，即使只是少量。有人可以帮助我了解为什么会这样吗？在此示例中，距离很小，但是在某些情况下，距离也可以足够大。

我对CSS比较陌生，所以我想知道如何解决这个问题。