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JavaScript implements image hierarchical carousel

王林

Release： 2023-05-26 15:54:38

Original

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In web design, image carousels are often used as an important display method on the page. In order to improve the user's browsing experience, we need an efficient and simple implementation method, and JavaScript is a good choice for implementing image carousels. This article will introduce how to use javascript to implement hierarchical carousel of images.

1. Brief description of the principle

The principle of hierarchical carousel of pictures is to display multiple pictures in a certain order. In order to ensure seamless switching, the pictures need to be displayed in layers, each time they are switched. , just move the top-level image to the bottom-level image to achieve carousel. Next, we will implement hierarchical carousel of images through javascript.

2. Implementation steps

1. Create HTML structure

Picture carousel needs to define a container element to contain all picture elements. Here we create a div element and specify its id as "container".

<div id="container">
   <img src="img/1.jpg" alt="">
   <img src="img/2.jpg" alt="">
   <img src="img/3.jpg" alt="">
   ...
</div>

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2. Set styles for container elements

In order to display the carousel smoothly, we need to set the width, height, and overflow:hidden attributes for the container element.

#container{
  width:800px;
  height:500px;
  overflow:hidden;
}

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3. Get the width of the picture element and container element

In order to achieve hierarchical carousel of pictures, we need to get the width of the picture element and container element. To obtain image elements through javascript, you can use the document.getElementsByTagName() method to obtain all images in the container.

var container = document.getElementById("container");
var imgs = container.getElementsByTagName("img");
var imgWidth = container.offsetWidth;

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4. Set the style of picture elements

In order to achieve hierarchical display of pictures, we need to absolutely position the picture elements and display them in layers. Put the first picture on the top layer, accumulate the z-index attribute value of the other pictures, and set the styles in sequence.

for(var i=0;i<imgs.length;i++){
  if(i==0){
    imgs[i].style.zIndex = "10";
  }else{
    imgs[i].style.zIndex = "10"+i;
  }
  imgs[i].style.position = "absolute";
  imgs[i].style.top = 0;
  imgs[i].style.left = imgWidth*i +"px";
}

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5. Animation effect settings

To achieve smooth transition of images, animation effects are required. Here we use the javascript timer (setInterval) to implement the carousel animation. In the timer, we move the first picture, and after the animation ends, move the first picture to the last display level. At the same time, by subtracting an imgWidth from the left value of other pictures, the overall smooth movement to the left is achieved.

var index = 0;
setInterval(function(){
  var next = (index+1)%imgs.length;
  imgs[index].style.left = 0-imgWidth +"px";
  imgs[index].style.zIndex = "10";
  imgs[next].style.left = imgWidth*(imgs.length-1)+"px";
  imgs[next].style.zIndex = "100";
  index=next;
},3000);

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3. Complete code

The final implemented code is as follows:

<html>
<head>
<style>
#container{
  width:800px;
  height:500px;
  overflow:hidden;
}
#container img{
  width:800px;
  height:500px;
}
</style>
</head>
<body>
   <div id="container">
     <img src="img/1.jpg" alt="">
     <img src="img/2.jpg" alt="">
     <img src="img/3.jpg" alt="">
     <img src="img/4.jpg" alt="">
     <img src="img/5.jpg" alt="">
   </div>
   <script>
      var container = document.getElementById("container");
      var imgs = container.getElementsByTagName("img");
      var imgWidth = container.offsetWidth;
      for(var i=0;i<imgs.length;i++){
        if(i==0){
          imgs[i].style.zIndex = "10";
        }else{
          imgs[i].style.zIndex = "10"+i;
        }
        imgs[i].style.position = "absolute";
        imgs[i].style.top = 0;
        imgs[i].style.left = imgWidth*i +"px";
      }
      var index = 0;
      setInterval(function(){
        var next = (index+1)%imgs.length;
        imgs[index].style.left = 0-imgWidth +"px";
        imgs[index].style.zIndex = "10";
        imgs[next].style.left = imgWidth*(imgs.length-1)+"px";
        imgs[next].style.zIndex = "100";
        index=next;
      },3000);
   </script>
</body>
</html>

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4. Summary

Using javascript to implement hierarchical carousel of images can improve the page display effect and user browsing experience. This article introduces the principle and implementation steps of image hierarchical carousel, and provides the complete code. I hope it will be helpful to everyone's learning and application.

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