How to use jQuery to implement carousel chart function

As the Internet content becomes more and more abundant, carousel images have become one of the standard features of many websites. The implementation methods of carousel graphs are also constantly updated. Among them, using jQuery to write carousel graphs has become a more popular method at present. So, this article will introduce to you how to use jQuery to implement a carousel chart.

1. HTML structure

First, let’s take a look at the HTML structure required to implement a carousel chart. Generally speaking, the HTML structure of a carousel chart can be divided into two parts: the carousel container and the carousel content. Among them, carousel content is generally implemented using ul and li tags.

<div>
    <ul>
        <li><img  src="/static/imghwm/default1.png" data-src="image1.jpg" class="lazy" alt="How to use jQuery to implement carousel chart function" ></li>
        <li><img  src="/static/imghwm/default1.png" data-src="image2.jpg" class="lazy" alt="How to use jQuery to implement carousel chart function" ></li>
        <li><img  src="/static/imghwm/default1.png" data-src="image3.jpg" class="lazy" alt="How to use jQuery to implement carousel chart function" ></li>
    </ul>
</div>

In the above code, we use a div container with a class name of swiper-container to contain the carousel image. In this container, we use a ul tag named swiper-wrapper to contain the content of the carousel. Each carousel item is implemented using a li tag with a class name of swiper-slide.

2. CSS Style

Next, we set the necessary CSS style for the carousel image. The main purpose is to optimize the style of the carousel container and carousel content so that they can be displayed correctly.

.swiper-container {
    position: relative;
    overflow: hidden;
}
.swiper-wrapper {
    width: 100%;
    position: relative;
    left: 0;
}
.swiper-slide {
    float: left;
    width: 100%;
    position: relative;
    font-size: 0;
    transition: all 0.3s linear;
}

Among them, we set the overflow attribute of the carousel container to hidden to hide the overflow part of the carousel image. At the same time, we set the position attribute of the carousel content to relative and the left attribute to 0 so that the carousel content can be displayed correctly. In addition, we set the float attribute of the carousel item to left and the width attribute to 100% so that the carousel item can be displayed correctly.

3. jQuery code implementation

After the HTML structure and CSS style are ready, we come to the most critical step, which is to use jQuery code to implement the carousel chart. During the implementation process, we need to operate the carousel container, carousel content, carousel items and other elements. The following is a simple jQuery code:

$(document).ready(function(){
    var index = 0; // 当前轮播项的索引值
    var len = $('.swiper-slide').length; // 轮播项的数量（此处为3个）
    var timer; // 定时器对象
    var interval = 3000; // 自动轮播的时间间隔

    // 首先将第一张图片设为当前的轮播项，并设置定时器，进行自动轮播
    $('.swiper-slide').eq(0).addClass('active');
    timer = setInterval(autoplay, interval);

    // 鼠标移入轮播容器时，暂停自动轮播
    $('.swiper-container').on('mouseenter', function(){
        clearInterval(timer);
    });

    // 鼠标移出轮播容器时，重新设置定时器，继续自动轮播
    $('.swiper-container').on('mouseleave', function(){
        timer = setInterval(autoplay, interval);
    });

    // 当点击小圆点时，切换到对应的轮播项
    $('.swiper-pagination li').on('click', function(){
        index = $(this).index();
        showImage(index);
    });

    // 左右箭头点击事件
    $('.swiper-btns .prev').on('click',function(){
        if(index=len-1){
            index=0;
        } else {
            index++;
        }
        showImage(index);
    })

    // 自动轮播方法
    function autoplay(){
        if(index>=len-1){
            index=0;
        } else {
            index++;
        }
        showImage(index);
    }

    // 显示指定的轮播项
    function showImage(index){
        $('.swiper-slide').eq(index).addClass('active').siblings().removeClass('active');
        $('.swiper-pagination li').eq(index).addClass('active').siblings().removeClass('active');
    }
});

In the above code, we mainly implement the following functions:

1. Set an index variable to record the index value of the current carousel item ;
2. Set a len variable to record the number of carousel items;
3. Set a timer variable to record the timer object of the carousel;
4. When the page is loaded , use the first picture as the current carousel item, and set a timer for automatic carousel;
5. When the mouse moves into the carousel container, the automatic carousel is paused;
6. The mouse moves out of the carousel container when, reset the timer and continue the automatic carousel;
7. When the small dot is clicked, switch to the corresponding carousel item;
8. Click events on the left and right arrows;
9. Automatic carousel Method, used to automatically play carousel items;
10. Display specified carousel items, used to display the items currently to be rotated.

To sum up, the above jQuery code can vividly and directly implement a simple carousel effect, and some key and practical jQuery methods and events are used in the implementation process. Understand these methods and events It has a positive role in optimizing front-end development and improving user experience.

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