锚点滚动功能干扰滚动事件监听器逻辑，使其无法显示 "返回顶部 "按钮。

Question

我已经建立了一个滚动到顶部的按钮，使用 这种方法 关于 本页.

我还写了一篇 function 来处理基于锚链接的滚动到章节的问题，以便在考虑到导航在顶部所占空间的情况下，将章节平滑地滚动到视口中。

这是一个重现这个问题的片段。

const navHeight = 42;
const $scrollTopBtn = $('#scroll-top-btn');

$(window).scroll(function() {
  const scrollTop = $(document).scrollTop();

  if (scrollTop > navHeight) {
    $scrollTopBtn.fadeIn();
  } else {
    $scrollTopBtn.fadeOut();
  }
});

$(document).ready(() => {
  $('a[href*="#"]').on('click', function(event) {
    const hash = this.hash;
    
    if (this.hash) {
      event.preventDefault();

      $('html, body').animate({
        scrollTop: $(hash).offset().top - navHeight,
      }, 350);

      window.location.hash = this.hash;
    }
  });
});

body {
  margin: 0;
  font-family: monospace;
}

nav {
  position: sticky;
  top: 0;
  display: flex;
  background: white;
  border-bottom: 2px solid black;
}

a {
  height: 40px;
  display: flex; 
  align-items: center; 
  padding: 0 8px;
  border-right: 2px solid black;
}

.block {
  min-height: 100vh;
  border-bottom: 2px solid black;
  display: flex; 
  justify-content: center;
  padding: 32px 50vw 32px 32px;
  box-sizing: border-box;
}

#scroll-top-btn {
  position: fixed;
  right: 8px;
  bottom: 8px;
  width: 40px;
  height: 40px;
  border: 2px solid black;
  display: flex; 
  align-items: center;
  justify-content: center;
  padding: 0;
  background: white;
}

<nav>
  <a href="#block1">Block 1</a>
  <a href="#block2">Block 2</a>
  <a href="#block3">Block 3</a>
</nav>

<div id="block1" class="block">
  Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
</div>

<div id="block2" class="block">
  Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo. Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem. Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit qui in ea voluptate velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum fugiat quo voluptas nulla pariatur?
</div>

<div id="block3" class="block">
  But I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system, and expound the actual teachings of the great explorer of the truth, the master-builder of human happiness. No one rejects, dislikes, or avoids pleasure itself, because it is pleasure, but because those who do not know how to pursue pleasure rationally encounter consequences that are extremely painful. Nor again is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtain some advantage from it? But who has any right to find fault with a man who chooses to enjoy a pleasure that has no annoying consequences, or one who avoids a pain that produces no resultant pleasure?
</div>

<button id="scroll-top-btn">👆</button>

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

在实际网站上，这个问题只发生在某些时候。当点击左侧导航的锚链接时，当页面滚动时，滚动到顶部按钮会短暂地闪烁。这很难复制，而且并不总是通过遵循相同的步骤发生，但它经常发生在第一次登陆FAQ页面并点击 "故障排除 "链接时。

如果我不运行锚点击滚动 function但按钮并不闪烁。

我不明白为什么按钮会闪烁，或者说它取决于什么，因为它应该在页面滚动超过导航的范围后才会消失 height (60px).

我也在使用 smoothState.js，这就要求我在 $(document).ready 并自行 onAfter 回调 function但滚动按钮监听器 function 只在 $(window).scroll.

可能是什么原因导致按钮闪烁的问题，如何解决？

Answer 1

那里发生的情况是，当你加载页面时，滚动位置会在最上面。然后，当你点击一个锚链接，你的平滑滚动代码开始缓慢滚动页面时，滚动监听器将被调用，但滚动位置仍将低于以下位置。navHeight因此，它将淡出（隐藏）了这一点。#scoll-top-btn 按钮，不久之后，滚动监听器将再次被调用，但这次的滚动位置将高于

不久之后，滚动监听器将再次被调用，但这次的滚动位置将高于 navHeight，所以它将淡入 #scoll-top-btn 按钮。

你可以通过检查滚动方向和滚动位置来解决这个问题，这样就可以使 #scoll-top-btn 按钮只有在向下滚动时才显示，或者只有在向上滚动时才隐藏。

另外，看起来你的 #scoll-top-btn 按钮最初是可见的，所以我将添加 style="display: none" 以使它在页面加载时总是被隐藏（但这本身并不能解决你的问题）。

在这里，你可以看到它是如何工作的两个变化应用。

const navHeight = 42;
const $scrollTopBtn = $('#scroll-top-btn');

let lastScrollTop = 0;

$(window).scroll(function() {
  const scrollTop = $(document).scrollTop();
  const scrollUp = scrollTop < lastScrollTop;

  lastScrollTop = scrollTop;

  if (scrollTop > navHeight && !scrollUp) {
    $scrollTopBtn.stop().fadeIn();
  } else if (scrollTop < navHeight && scrollUp) {
    $scrollTopBtn.stop().fadeOut();
  }
});

$(document).ready(() => {
  $('a[href*="#"]').on('click', function(event) {
    const hash = this.hash;
    
    if (this.hash) {
      event.preventDefault();

      $('html, body').animate({
        scrollTop: $(hash).offset().top - navHeight,
      }, 350);

      window.location.hash = this.hash;
    }
  });
});

body {
  margin: 0;
  font-family: monospace;
}

nav {
  position: sticky;
  top: 0;
  display: flex;
  background: white;
  border-bottom: 2px solid black;
}

a {
  height: 40px;
  display: flex; 
  align-items: center; 
  padding: 0 8px;
  border-right: 2px solid black;
}

.block {
  min-height: 100vh;
  border-bottom: 2px solid black;
  display: flex; 
  justify-content: center;
  padding: 32px 50vw 32px 32px;
  box-sizing: border-box;
}

#scroll-top-btn {
  position: fixed;
  right: 8px;
  bottom: 8px;
  width: 40px;
  height: 40px;
  border: 2px solid black;
  display: flex; 
  align-items: center;
  justify-content: center;
  padding: 0;
  background: white;
}

<nav>
  <a href="#block1">Block 1</a>
  <a href="#block2">Block 2</a>
  <a href="#block3">Block 3</a>
</nav>

<div id="block1" class="block">
  Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
</div>

<div id="block2" class="block">
  Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo. Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem. Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit qui in ea voluptate velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum fugiat quo voluptas nulla pariatur?
</div>

<div id="block3" class="block">
  But I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system, and expound the actual teachings of the great explorer of the truth, the master-builder of human happiness. No one rejects, dislikes, or avoids pleasure itself, because it is pleasure, but because those who do not know how to pursue pleasure rationally encounter consequences that are extremely painful. Nor again is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtain some advantage from it? But who has any right to find fault with a man who chooses to enjoy a pleasure that has no annoying consequences, or one who avoids a pain that produces no resultant pleasure?
</div>

<button id="scroll-top-btn" style="display: none">👆</button>

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>