Native js to achieve seamless carousel effect

Native js realizes the carousel effect (seamless scrolling) for your reference. The specific content is as follows

Effect picture:

Code:

<!DOCTYPE html>
<html lang="en">
<!-- day07 7-10-14 -->
 
<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>Document</title>
 <script src="./images1/20.animate.js"></script>
 <style>
 * {
  margin: 0;
  padding: 0;
 }
 
 li {
  list-style: none;
 }
 
 .focus {
  /*overflow: hidden;*/
  position: absolute;
  top: 100px;
  left: 200px;
  width: 721px;
  height: 455px;
  background-color: brown;
 }
 
 .prev,
 .next {
  display: none;
  position: absolute;
  top: 50%;
  margin-top: -15px;
  width: 20px;
  height: 30px;
  background-color: rgba(0, 0, 0, .3);
  text-decoration: none;
  color: #fff;
  line-height: 30px;
  text-align: center;
  font-size: 16px;
  z-index: 2;
 }
 
 .focus ul {
  /* The introduction of animation js files requires positioning*/
  position: absolute;
  width: 600%;
 }
 
 .focus ul li {
  float: left;
 }
 
 .prev {
  left: 0;
  border-top-right-radius: 15px;
  border-bottom-right-radius: 15px;
 }
 
 .next {
  right: 0;
  border-top-left-radius: 15px;
  border-bottom-left-radius: 15px;
 }
 
 .promo-nav {
  position: absolute;
  bottom: 10px;
  left: 60px;
  width: 200px;
  height: 18px;
  border-radius: 9px;
 }
 
 .promo-nav li {
  float: left;
  width: 10px;
  height: 10px;
  background-color: #fff;
  margin: 2px;
  border-radius: 50%;
 }
 
 .promo-nav .current {
  background-color: orange;
 }
 .focus ul li a img {
  width: 721px;
  height: 455px;
 }
 </style>
</head>
 
<body>
 <div class="focus">
 <ul>
  <li>
  <a href="#" ><img src="images1/focu01.jpg" alt=""></a>
  </li>
  <li>
  <a href="#" ><img src="images1/focu02.jpg" alt=""></a>
  </li>
 
  <li>
  <a href="#" ><img src="images1/focu03.jpg" alt=""></a>
  </li>
  <li>
  <a href="#" ><img src="images1/focu04.jpg" alt=""></a>
  </li>
 
 </ul>
 <!-- Left button -->
 <a href="javascript:;" class="prev">&lt;</a>
 <!-- Right button -->
 <a href="javascript:;" class="next">&gt;</a>
 
 <ol class="promo-nav">
 
 </ol>
 </div>
 <script>
 window.addEventListener('load', function() {
  var focus = document.querySelector('.focus');
  var prev = document.querySelector('.prev');
  var next = document.querySelector('.next');
  var focusWidth = focus.offsetWidth;
  //The mouse passes through focus.addEventListener('mouseenter', function() {
   prev.style.display = 'block';
   next.style.display = 'block';
   clearInterval(timer);
   timer = null; // clear the timer variable })
  //The mouse leaves focus.addEventListener('mouseleave', function() {
   prev.style.display = 'none';
   next.style.display = 'none';
   timer = setInterval(function() {
   next.click();
   }, 2000)
 
  })
  //3. Dynamically generate small circles. Generate as many small circles as there are pictures. var ul = focus.querySelector('ul');
  var ol = focus.querySelector('.promo-nav');
  // console.log(ul.children.length); 4
  for (var i = 0; i < ul.children.length; i++) {
  //Create a li
  var li = document.createElement('li');
  //Record the index number of the current small circle through custom attributes li.setAttribute('index', i);
  //Insert after ol ol.appendChild(li);
  //4. Click the small circle with the mouse to change its color (add the current class to the small circle and remove this class from the other small circles) (exclusive idea)
  //Directly bind the click event while generating the small circle li.addEventListener('click', function() {
   for (var i = 0; i < ol.children.length; i++) {
   ol.children[i].className = '';
   }
   this.className = 'current';
 
 
   //5. Click the small dot to move the picture. The ul is moved.
   //The distance ul moves is the index number of the small circle multiplied by the width of the image. Note that it is a negative value. //When we click on a small li, we get the index number of the current small li. var index = this.getAttribute('index');
   //When we click on a certain li, we give the index number of li to num
   num = index;
   //When we click on a certain li, we give the index number of li to index
   circle = index;
   console.log(index);
 
   animate(ul, -index * focusWidth, );
  })
 
  }
  //Set the color of the first li in ol to white ol.children[0].className = 'current';
  //6. Clone the first li and put it behind ul var first = ul.children[0].cloneNode(true);
  ul.appendChild(first);
  //7. Click the button on the right to scroll one picture var num = 0;
  var circle = 0;
  var flag = true;
  //Right button next.addEventListener('click', function() {
   if (flag) {
   flag = false; //Close the throttle first //5. If you reach the last copied image, ul will quickly restore left to 0 (seamless scrolling)
   if (num == ul.children.length - 1) {
    ul.style.left = 0;
    num = 0;
   }
   num++;
   animate(ul, -num * focusWidth, function() {
    flag = true;
   });
   //8. Click the button on the right and the small circle will change accordingly. Declare a variable to control the change of the small circle circle++;
   //If circle is equal to 4, it means that we have finished cloning the last picture and we will restore it if (circle == ol.children.length) {
    circle = 0;
   }
   // //Clear the remaining small circle class names// for (var i = 0; i < ol.children.length; i++) {
   // ol.children[i].className = '';
   // }
   // //Leave the current small circle current class name// ol.children[circle].className = 'current';
   circleChange();
   }
  })
  //Left button prev.addEventListener('click', function() {
  if (flag) {
   flag = false;
   //5. If you reach the last copied image, ul will quickly restore left to 0 (seamless scrolling)
   if (num == 0) {
   num = ul.children.length - 1;
   ul.style.left = -num * focusWidth + 'px';
 
   }
   num--;
   animate(ul, -num * focusWidth, function() {
   flag = true;
   });
   //8. Click the button on the right and the small circle will change accordingly. Declare a variable to control the change of the small circle circle--;
   //If circle is less than 0, the small circle will be changed to the fourth small circle if (circle < 0) {
   circle = ol.children.length - 1;
   }
   // Clear the remaining small circle class names // for (var i = 0; i < ol.children.length; i++) {
   // ol.children[i].className = '';
   // }
   // Leave the current small circle current class name // ol.children[circle].className = 'current';
   circleChange();
  }
  })
 
  function circleChange() {
  //Clear the rest of the small circle class names for (var i = 0; i < ol.children.length; i++) {
   ol.children[i].className = '';
  }
  //Leave the current small circle current class name ol.children[circle].className = 'current';
  }
 
  //10. Automatically play the slideshow var timer = setInterval(function() {
  next.click();
  }, 2000)
 
 })
 </script>
</body>
 
</html>

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