常见轮播效果及其实现原理

说明： 本项目只做最基础的原理分析与最简单的应用场景。

思路： 在同一个父容器内，
1. 通过改变父容器的`left` 值实现---视图切换，
2. 通过补充边界视图的过渡状态，外观上实现---无缝滚动。

核心代码：custom-carsoul.html || simple-slide.html

//css
 #container {
 width: 600px;
 height: 400px;
 border: 3px solid #333;
 overflow: hidden;
 position: relative;
    }

    #list {
 width: 3000px;
 height: 400px;
 position: absolute;
 z-index: 1;
    }

 #list div {
 float: left;
 display: flex;
 justify-content: center;
 background: #ccc;
 width: 600px;
 height: 300px;
    }

//js

var go = function() {
  if ((speed > 0 && parseInt(list.style.left) < left) || (speed < 0 && parseInt(list.style.left) > left)) {
      list.style.left = parseInt(list.style.left) + speed + 'px';
      setTimeout(go, inteval);
  } else {
      list.style.left = left + 'px';
      if (left > -200) {
   list.style.left = -600 * len + 'px';
      }
      if (left < (-600 * len)) {
   list.style.left = '-600px';
      }
      animated = false;
  }
     }

思路： 在同一个父容器内，
1. 通过改变各个仕途的过渡渐变，实现

核心代码：css3-transition.html

//css

#slideshow img {
 width: 800px;
 position: absolute;
 top: 0;
 left: 0;
 opacity: 0;
 transition: opacity 1s linear;
    }

    #slideshow img.active {
 opacity: 1;
    }

思路： 在同一个父容器内，
1. 通过各个视图切换动画实现

核心代码：css-animate.html

//css

@keyframes slide {
 0% {
     background-position: 0 0;
 }
 10%, 25% {
     background-position: -600px 0;
 }
 35%, 50% {
     background-position: -1200px 0;
 }
 60%, 75% {
     background-position: -1800px 0;
 }
 85%, 100% {
     background-position: 0 0;
 }
    }

思路： 在同一个父容器内，
1. 将各个视图围成正棱柱体，
2. 改变正棱柱体旋转角度及视口距离，而实现无限滚动轮播

核心代码：3d-transform.html

//css
 .container {
 width: 150%;
 height: 100px;
 transition: transform 1s;
 transform-style: preserve-3d;
 position: absolute;
    }

//js

function transform(element, value) {
     return element.style['transform'] = value;
 }
//50 为调整值
 transZ = 50/ Math.tan((rotate / 2 / 180) * Math.PI);

思路： 在同一个父容器内，

   1. 重点难点在于css3的过渡与渐变的应用；
   2. 临界状态过渡处理；
   3. 活动元素class：active->active left||right->'',下一个活动元素class：next left || prev right->active；

1. 同一次状态只改变两个元素的class属性；

核心代码：bootstrap-carsoul.html

//css
    
    .carousel-inner>.item {
 position: relative;
 display: none;
 transition: transform .6s ease-in-out;
    }
    
    .carousel-inner>.active,
    .carousel-inner>.next,
    .carousel-inner>.prev {
 display: block;
    }
    
    .carousel-inner>.item.active,
    .carousel-inner>.item.next.left,
    .carousel-inner>.item.prev.right {
 left: 0;
 transform: translate3d(0, 0, 0);
    }
    
    .carousel-inner>.item.active.left,
    .carousel-inner>.item.prev {
 left: 0;
 transform: translate3d(-100%, 0, 0);
    }
    .carousel-inner>.item.active.right,
    .carousel-inner>.item.next {
 left: 0;
 transform: translate3d(100%, 0, 0);
    }
//js(mocking up)
    window.onload = function() {
      var items = document.querySelectorAll('.carousel-inner .item');
      var prev = document.querySelector('#prev');
      var next = document.querySelector('#next');
      var animated = false;
      var cur = 0;
      var duration = 600;

      function moveTo(i) {
 animated = true;
 if (i > 0) {
   cur = cur === 2 ? 0 : cur + i;
   var cLeft = cur - i === -1 ? 2 : cur - i;
   transition(cur, cLeft, 'next', 'left')
 } else {
   cur = cur === 0 ? 2 : cur + i;
   var cRight = cur - i === 3 ? 0 : cur - i;
   transition(cur, cRight, 'prev', 'right')
 }

 function transition(cur, cx, order, direction) {
   items[cx].classList.add(direction);
   items[cur].classList.add(order, direction);
   setTimeout(() => {
     items[cx].classList.remove('active', direction);
     items[cur].classList.remove(order, direction);
     items[cur].classList.add('active');
     animated = false;
   }, duration);
 }
      }
      prev.onclick = function() {
 if (animated) {
   return
 }
 moveTo(-1);
      }
      next.onclick = function() {
 if (animated) {
   return
 }
 moveTo(1);
      }
    }

思路： 在同一个父容器内，
1. 活动元素显示，非活动元素过渡切换状态

核心代码：bootstrap-carsoul.html

//css
    
    .carousel-inner>.item {
 position: relative;
 display: none;
 transition: transform .6s ease-in-out;
    }
    
    .carousel-inner>.active,
    .carousel-inner>.next,
    .carousel-inner>.prev {
 display: block;
    }
    
    .carousel-inner>.item.active,
    .carousel-inner>.item.next.left,
    .carousel-inner>.item.prev.right {
 left: 0;
 transform: translate3d(0, 0, 0);
    }
    
    .carousel-inner>.item.active.left,
    .carousel-inner>.item.prev {
 left: 0;
 transform: translate3d(-100%, 0, 0);
    }
    .carousel-inner>.item.active.right,
    .carousel-inner>.item.next {
 left: 0;
 transform: translate3d(100%, 0, 0);
    }
//js