滚动错误时的主动导航 - Vanilla JS

Question

I'm trying to make an active state nav menu were the anchor links are highlighted once they're scrolled to each section. I just tested my site and received the following errors:

Uncaught DOMException: Failed to execute 'querySelector' on 'Document': The provided selector is empty.

NodeList.forEach ()

The errors are for this code:

navLinks.forEach(link => {
    let section = document.querySelector(link.hash);

I've never seen these before and I'm confused as to what I should do. Thank you!

--HTML--
<div class="menu">
<div class="top-nav">
<div class="logo">
<h1>Store</h1>
</div>
<div class="close">
<i class="bx bx-x"></i>
</div>
</div>
<ul class="nav-list">
<li class="nav-item"><a class="nav-link active" href="#home">Home</a></li>
<li class="nav-item"><a href="#products" class="nav-link">Products</a></li>
<li class="nav-item"><a href="#featured" class="nav-link">Featured</a></li>
<li class="nav-item"><a href="#best-sellers" class="nav-link">Best Sellers</a></li>
<li class="nav-item"><a href="#contact" class="nav-link">Contact</a></li>
<li class="nav-item"><a href="#" class="nav-link icon"><i class="bx bx-shopping-bag"></i></a></li>
</ul>
</div>

<main>
<section class="section featured">
   <div class="title">
      <h1 id="products">Products</h1>
   </div>
</section>

<section class="section featured">
   <div class="title">
      <h1 id="featured">Featured</h1>
   </div>

</section>
<section class="section featured">
   <div class="title">
      <h1 id="best-sellers">Best Sellers</h1>
   </div>
</section>
</main> 

<footer id="footer" class="section footer">
   <div class="footer-title">
      <h1 id="contact">Contact</h1>
   </div>
</footer>

--JS--
//Change navigation style on scroll
window.addEventListener('scroll', event => { 
    let scrollLink = document.querySelector('a.nav-link'); 
    
    (window.scrollY >= 45) ? scrollLink.classList.add('scroll') : scrollLink.classList.remove('scroll');
});

//Active navigation on scroll
window.addEventListener('scroll', event => {
  let navLinks = document.querySelectorAll('a');
  let fromTop = window.scrollY;
 
  navLinks.forEach(link => {
    let section = document.querySelector(link.hash);
   
    if (
      section.offsetTop <= fromTop &&
      section.offsetTop + section.offsetHeight > fromTop
    ) {
      link.classList.add('active');
    } else {
      link.classList.remove('active');
    }
  });
});

--CSS--
a {
    color: inherit;
    text-decoration: none;
}

a:hover,
a:focus {
    color: #fa448c;
    text-decoration: underline;
}

a.active {
    padding: 8px 15px;
    display: block;
    text-transform: capitalize;
    background-color: #fa448c;
    color: #fff;
}

li {
    list-style-type: none;
}

Answer 1

This code means that the number of sections must correspond to the number of tags a .

I corrected your code a bit, and also commented out the first and last a tag. See how it works. But there is no need to stop there. It is necessary to exclude the first and last tag when accessing, using method querySelectorAll(".nav-list a") .

 let mainNavLinks = document.querySelectorAll(".nav-list a"); window.addEventListener("scroll", event => { let fromTop = window.scrollY; mainNavLinks.forEach(link => { let section = document.querySelector(link.hash); if ( section.offsetTop <= fromTop && section.offsetTop + section.offsetHeight > fromTop ) { link.classList.add("active"); } else { link.classList.remove("active"); } }); });

 .menu { position: sticky; top: 0; background-color: white; } a { color: inherit; text-decoration: none; } a:hover, a:focus { color: #fa448c; text-decoration: underline; }.active { padding: 8px 15px; display: block; text-transform: capitalize; background-color: #fa448c; color: #fff; } li { list-style-type: none; } #products { background-color: red; height: 500px; } #featured { background-color: green; height: 500px; } #best-sellers { background-color: yellow; height: 500px; } #contact { background-color: grey; height: 500px; }

 --HTML-- <div class="menu"> <div class="top-nav"> <div class="logo"> <h1>Store</h1> </div> <div class="close"> <i class="bx bx-x"></i> </div> </div> <ul class="nav-list"> <,--li class="nav-item"><a class="nav-link active" class="home" href="#home">Home</a></li--> <li class="nav-item"><a href="#products" class="nav-link">Products</a></li> <li class="nav-item"><a href="#featured" class="nav-link">Featured</a></li> <li class="nav-item"><a href="#best-sellers" class="nav-link">Best Sellers</a></li> <li class="nav-item"><a href="#contact" class="nav-link">Contact</a></li> <,--li class="nav-item"><a href="#" class="nav-link icon"><i class="bx bx-shopping-bag"></i></a></li--> </ul> </div> <div class="sections"> <div id="products">"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> <div id="featured">"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> <div id="best-sellers">"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> <div id="contact">"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> </div>