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JS banner无限滚动 原生JS利用transform实现banner的无限滚动代码实例

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功能

原理

首先说下原理。

这种方法也可以做到整个页面始终只有2个img标签,而不必把所有的img节点全部创建出来,要点是每次更换不可见img的src。

动画的实现

这样就完成了一次移动的动画。

html代码

<header>
  <div class="box">
    <img src="imgs/banner1.jpg">
    <img src="imgs/banner2.jpg">
    <img src="imgs/banner3.jpg">
    <img src="imgs/banner4.jpg">
  </div>
  <div class="buttons">
    <div class="active">1</div>
    <div>2</div>
    <div>3</div>
    <div>4</div>
  </div>
  <div class="left">
    <div class="arrow"></div>
  </div>
  <div class="right">
    <div class="arrow"></div>
  </div>
</header>

JS代码

var timeout = null;
window.onload = function () {
  var oLeft = document.querySelector('.left');
  var oRight = document.querySelector('.right');
  var oButton = document.querySelector('.buttons');
  var oButtons = document.querySelectorAll('.buttons div');
  var oImgs = document.querySelectorAll('.box img');
  var imgWidth = oImgs[0].width;
  var gIndex = 0;
  begainAnimate();

  // 绑定左右点击事件
  oLeft.onclick = function () {
    clearTimeout(timeout);
    leftMove();
    begainAnimate();
  };
  oRight.onclick = function () {
    clearTimeout(timeout);
    rightMove();
    begainAnimate();
  };
  // 绑定数字序号事件
  oButton.onclick = function (event) {
    clearTimeout(timeout);
    var targetEl = event.target;
    var nextIndex = (+targetEl.innerText) - 1;
    console.log(nextIndex);
    rightMove(nextIndex);
    begainAnimate();
  }
  // 默认初始动画朝右边
  function begainAnimate() {
    clearTimeout(timeout);
    timeout = setTimeout(function () {
      rightMove();
      begainAnimate();
    }, 3000);
  }
  // 向左移动动画
  function leftMove() {
    var nextIndex = (gIndex - 1 < 0) ? oImgs.length - 1 : gIndex - 1;
    animateSteps(nextIndex, -50);
  }
  // 向右移动动画
  function rightMove(nextIndex) {
    if (nextIndex == undefined) {
      nextIndex = (gIndex + 1 >= oImgs.length) ? 0 : gIndex + 1;
    }
    animateSteps(nextIndex, 50);
  }
  // 一次动画
  function animateSteps(nextIndex, timestamp) {
    var currentImg = oImgs[gIndex];
    var nextImg = oImgs[nextIndex];
    nextImg.style.zIndex = 10;
    var step = 0;
    requestAnimationFrame(goStep);
    // 走一帧的动画,移动timestamp
    function goStep() {
      var moveWidth = timestamp * step++;
      if (Math.abs(moveWidth) < imgWidth) {
        currentImg.style.transform = `translate(${moveWidth}px)`;
        nextImg.style.transform = `translate(${moveWidth > 0 ? (moveWidth - imgWidth) : (imgWidth + moveWidth)}px)`;
        requestAnimationFrame(goStep);
      } else {
        currentImg.style.zIndex = 1;
        currentImg.style.transform = `translate(0px)`;
        nextImg.style.transform = `translate(0px)`;
        oButtons[gIndex].setAttribute('class', '');
        oButtons[nextIndex].setAttribute('class', 'active');
        gIndex = nextIndex;
      }
    }
  }
}
window.onclose = function () {
  clearTimeout(timeout);
}

css布局样式

<style>
  /* 首先设置图片box的区域,将图片重叠在一起 */
  header {
    width: 100%;
    position: relative;
    overflow: hidden;
  }
  .box {
    width: 100%;
    height: 300px;
  }
  .box img {
    width: 100%;
    height: 100%;
    position: absolute;
    transform: translateX(0);
    z-index: 1;
  }
  .box img:first-child {
    z-index: 10;
  }
  
  /* 数字序列按钮 */
  .buttons {
    position: absolute;
    right: 10%;
    bottom: 5%;
    display: flex;
    z-index: 100;
  }

  .buttons div {
    width: 30px;
    height: 30px;
    background-color: #aaa;
    border: 1px solid #aaa;
    text-align: center;
    margin: 10px;
    cursor: pointer;
    opacity: .7;
    border-radius: 15px;
    line-height: 30px;
  }

  .buttons div.active {
    background-color: white;
  }

  /* 左右切换按钮 */
  .left,
  .right {
    position: absolute;
    width: 80px;
    height: 80px;
    background-color: #ccc;
    z-index: 100;
    top: 110px;
    border-radius: 40px;
    opacity: .5;
    cursor: pointer;
  }

  .left {
    left: 2%;
  }

  .right {
    right: 2%;
  }

  .left .arrow {
    width: 30px;
    height: 30px;
    border-left: solid 5px #666;
    border-top: solid 5px #666;
    transform: translate(-5px, 25px) rotate(-45deg) translate(25px, 25px);
  }

  .right .arrow {
    width: 30px;
    height: 30px;
    border-left: solid 5px #666;
    border-top: solid 5px #666;
    transform: translate(50px, 25px) rotate(135deg) translate(25px, 25px);
  }
</style>

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