25-Sticky-Navigation（吸附导航栏）

滚动后

html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <title>Document</title>
</head>
<body>
    <nav class="nav">
        <div class="container">
            <h1 class="logo">
                <a href="/index.html">My Website</a>
            </h1>
            <ul>
                <li><a href="" class="current">Home</a></li>
                <li><a href="">About</a></li>
                <li><a href="">Services</a></li>
                <li><a href="">Contact</a></li>   
            </ul>
        </div>
    </nav>

    <div class="hero">
        <div class="conatiner">
            <h1>Welcome To My Website</h1>
        <p>Lorem ipsum, dolor sit amet consectetur adipisicing elit. Maiores, consequuntur?</p>
        </div>
    </div>

    <section class="container content">
        <h2>Content One</h2>
        <p>Lorem, ipsum dolor sit amet consectetur adipisicing elit. Ratione dolorem voluptates eveniet tempora ut cupiditate magnam, sapiente, hic quo in ipsum iste soluta eaque perferendis nihil recusandae dolore officia aperiam corporis similique. Facilis quos tempore labore totam! Consectetur molestiae iusto ducimus error reiciendis aspernatur dolor, modi dolorem sit architecto, voluptate magni sunt unde est quas? Voluptates a dolorum voluptatum quo perferendis aut sit. Aspernatur libero laboriosam ab eligendi omnis delectus earum labore, placeat officiis sint illum rem voluptas ipsum repellendus iste eius recusandae quae excepturi facere, iure rerum sequi? Illum velit delectus dicta et iste dolorum obcaecati minus odio eligendi!</p>
  
        <h3>Content Two</h3>
        <p>Lorem ipsum dolor sit amet consectetur, adipisicing elit. Pariatur provident nostrum possimus inventore nisi laboriosam consequatur modi nulla eos, commodi, omnis distinctio! Maxime distinctio impedit provident, voluptates illo odio nostrum minima beatae similique a sint sapiente voluptatum atque optio illum est! Tenetur tempora doloremque quae iste aperiam hic cumque repellat?</p>
      </section>




    <script src="script.js"></script>
</body>
</html>

css

@import url('https://fonts.googleapis.com/css?family=Open+Sans');

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
    font-family: 'Open Sans', sans-serif;
    color: #222;
    padding-bottom: 50px;
  }

  .container{
    max-width: 1200px;
    margin: 0 auto;
  }

  .nav{
    position: fixed;
    background-color: #222;
    top: 0;
    left: 0;
    right: 0;
    transition: all 0.3s ease-in-out;
  }

  .nav .container{
    display: flex;
    justify-content: space-between;
    padding: 20px 0;
    transition: all 0.3s ease-in-out;
  }

  .nav ul{
    display: flex;
    list-style-type: none;
    align-items: center;
    justify-content: center;
  }
  .nav a{
    color: #fff;
    text-decoration: none;
    padding: 7px 15px;
    transition: all 0.3s ease-in-out;
  }

  .nav.active{
    background-color: #fff;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
  }

  .nav.active a{
    color: #000;
  }

  .nav.active .container{
    padding: 10px 0;
  }

  .nav a.current,
  .nav a:hover{
    color: #c0392b;
    font-weight: bold;
  }

  .hero{
    background-image: url('https://images.pexels.com/photos/450035/pexels-photo-450035.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=750&w=1260');
    background-repeat: no-repeat;
    background-size: cover;
    background-position: bottom center;
    height: 100vh;
    color: #fff;
    display: flex;
    justify-content: center;
    align-items: center;
    text-align: center;
    position: relative;
    margin-bottom: 20px;
    z-index:-2;
  }

  .hero::before{
    content:'';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: -1;
  }

  .hero h1 {
    font-size: 46px;
    margin: -20px 0 20px;
  }
  
  .hero p {
    font-size: 20px;
    letter-spacing: 1px;
  }
  
  .content h2,
  .content h3 {
    font-size: 150%;
    margin: 20px 0;
  }
  
  .content p {
    color: #555;
    line-height: 30px;
    letter-spacing: 1.2px;
  }

const nav=document.querySelector('.nav')
window.addEventListener('scroll',fixNav)

function fixNav(){
    if(window.scrollY>nav.offsetHeight+150){
        nav.classList.add('active');
    }else{
        nav.classList.remove('active');
    }
}