50天50个前端小项目（纯html+css+js）第十八天（背景轮播图）

news2025/2/25 0:25:12

今天要做的是一个轮播图，不过是属于全屏类型的轮播图，先来看看效果：
在这里插入图片描述

点击左右按钮能切换背景，达到轮播图效果

来看代码实现部分，首先是html:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link
      rel="stylesheet"
      href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.14.0/css/all.min.css"
      integrity="sha512-1PKOgIY59xJ8Co8+NE6FZ+LOAZKjy+KY8iq0G4B3CyeY6wYHN3yt9PW0XpSriVlkMXe40PTKnXrLnZ9+fkDaog=="
      crossorigin="anonymous"
    />
    <link rel="stylesheet" href="style.css" />
    <title>Background Slider</title>
  </head>
  <body>
    <div class="slider-container">
      <div
        class="slide active"
        style="
          background-image: url('https://images.unsplash.com/photo-1549880338-65ddcdfd017b?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=2100&q=80');
        "
      ></div>
      <div
        class="slide"
        style="
          background-image: url('https://images.unsplash.com/photo-1511593358241-7eea1f3c84e5?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=1934&q=80');
        "
      ></div>

      <div
        class="slide"
        style="
          background-image: url('https://images.unsplash.com/photo-1495467033336-2effd8753d51?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=2100&q=80');
        "
      ></div>

      <div
        class="slide"
        style="
          background-image: url('https://images.unsplash.com/photo-1522735338363-cc7313be0ae0?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=2689&q=80');
        "
      ></div>

      <div
        class="slide"
        style="
          background-image: url('https://images.unsplash.com/photo-1559087867-ce4c91325525?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=2100&q=80');
        "
      ></div>
        <!-- 左滑块按钮 -->
      <button class="arrow left-arrow" id="left">
        <i class="fas fa-arrow-left"></i>
      </button>
      <!-- 右滑块按钮 -->
      <button class="arrow right-arrow" id="right">
        <i class="fas fa-arrow-right"></i>
      </button>
    </div>
    <script src="script.js"></script>
  </body>
</html>

这里面没啥，就是几张图片，以及左右两个按钮的布局。

再来看css:
这里面的重点是蒙层，以及图片在默认的时候不显示，而在到它的时候就赋上active值让其显示。

* {
  box-sizing: border-box;
}

body {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100vh;
  overflow: hidden;
  margin: 0;
  background-position: center center;
  background-size: cover;
  transition: 0.4s;
}

/* 添加一个蒙层 */
body::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100vh;
  background-color: rgba(0, 0, 0, 0.7);
  /* 防止覆盖住按钮 */
  z-index: -1;
}

/* 小的滑框 */
.slider-container {
  box-shadow: 0 3px 6px rgba(0, 0, 0, 0.16), 0 3px 6px rgba(0, 0, 0, 0.23);
  height: 70vh;
  width: 70vw;
  position: relative;
  /* 溢出内容隐藏 */
  overflow: hidden;
}

/* 默认的时候背景图片 */
.slide {
  opacity: 0;
  height: 100vh;
  width: 100vw;
  background-position: center center;
  background-size: cover;
  position: absolute;
  top: -15vh;
  left: -15vw;
  transition: 0.4s ease;
  z-index: 1;
}


.slide.active {
  opacity: 1;
}

/* 按钮 */
.arrow {
  position: fixed;
  background-color: transparent; 
  color: #fff;
  padding: 20px;
  font-size: 30px;
  border: 2px solid orange;
  top: 50%;
  transform: translateY(-50%);
  cursor: pointer;
}

/* 去掉轮廓 */
.arrow:focus {
  outline: 0;
}

/* 左右按钮的位置 */
.left-arrow {
  left: calc(15vw - 65px);
}

.right-arrow {
  right: calc(15vw - 65px);
}

再来看JavaScript部分：

const body = document.body
const slides = document.querySelectorAll('.slide')
const leftBtn = document.getElementById('left')
const rightBtn = document.getElementById('right')

// 一开始默认下标为0，即显示第一张
let activeSlide = 0

// 左边的滑块，下标++，即下一张图片
rightBtn.addEventListener('click', () => {
  activeSlide++

//   最后一张再往后就直接到第一张
  if (activeSlide > slides.length - 1) {
    activeSlide = 0
  }

  setBgToBody()
  setActiveSlide()
})

// 右边的滑块，下标--，即上一张图片
leftBtn.addEventListener('click', () => {
  activeSlide--

//   到第一张之后再上一张就到最后一张
  if (activeSlide < 0) {
    activeSlide = slides.length - 1
  }

  setBgToBody()
  setActiveSlide()
})

setBgToBody()

// 改变背景图片
function setBgToBody() {
  body.style.backgroundImage = slides[activeSlide].style.backgroundImage
}

// 到哪个图片的下标后就给它加上active，就能让图片opacity为1显示
/* 当前opacity为1显示之后其他的就为0了 */
function setActiveSlide() {
  slides.forEach((slide) => slide.classList.remove('active'))

  slides[activeSlide].classList.add('active')
}