JavaScript实现无缝图片轮播：左右切换与自动播放详解

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Carousel chart</title>
    <link rel="stylesheet" href="./style.css" >
    <script src="./index.js"></script>
    <script src="./animate.js"></script>
</head>

<body>
    <div class="carousel_box" id="carousel-box">
        <a href="javascript:;" class="arrow-l">
            < </a>
                <a href="javascript:;" class="arrow-r"> > </a>
                <ul class="move">
                    <li><img src="./images/xuezhong_1.jpg" alt=""></li>
                    <li><img src="./images/guimizhizhu_2.jpg" alt=""></li>
                    <li><img src="./images/jianlai_3.jpg" alt=""></li>
                    <li><img src="./images/yichang_4.jpg" alt=""></li>
                </ul>
                <ol class="circle">
                </ol>
    </div>
</body>

</html>

*{
    padding: 0;
    margin: 0;
}

li {
    list-style-type: none;
}

#carousel-box {
    position: relative;
    width: 700px;
    height: 300px;
    background-color: pink;
    margin: 100px auto;
    overflow: hidden;
}

.arrow-l,.arrow-r {
    display: none;
    position:absolute;
    width: 24px;
    height: 40px;
    top: 50%;
    margin-top: -20px;
    background: rgba(0, 0, 0, 0.3);
    text-align:center;
    line-height: 40px;
    color: #fff;
    font-size: 18px;
    font-family: 'icomoon';
    z-index: 3;
}
.arrow-r {
    right: 0;
}

#carousel-box img{
    width: 700px;
    height: 300px;
}

#carousel-box ul {
    position:absolute;
    width: 1000%;
}

#carousel-box ul li {
    float: left;
}

.circle {
    position: absolute;
    bottom: 10px;
    right: 10px;
}

.circle li {
    float: left;
    width: 8px;
    height: 8px;
    margin: 0 5px;
    border: 2px solid rgba(255, 255, 255, 0.5);
    border-radius: 50%;
    cursor: pointer;
    z-index: 9999;
}

.current {
    background-color: pink;
}

function animate(obj, target, callback) {
    clearInterval(obj.timer);
    obj.timer = setInterval(function () {
        /* 判断正负，小数取大还是取小 */
        var step = (target - obj.offsetLeft) / 10;
        step = step > 0 ? Math.ceil(step) : Math.floor(step);

        if (obj.offsetLeft == target) {
            clearInterval(obj.timer);
            callback && callback();
        }
        obj.style.left = obj.offsetLeft + step + 'px';
    }, 15);
}

window.addEventListener('load', function () {
    var carousel = document.querySelector('.carousel_box');
    var ul = document.querySelector('.move');
    var ol = document.querySelector('.circle');
    var carcouselWidth = carousel.offsetWidth;
    var arrow_l = document.querySelector('.arrow-l');
    var arrow_r = document.querySelector('.arrow-r');

    carousel.addEventListener('mouseenter', function () {
        arrow_r.style.display = 'block';
        arrow_l.style.display = 'block';
        clearInterval(timer);
        timer = null; // 清除定时器变量
    })

    carousel.addEventListener('mouseleave', function () {
        arrow_r.style.display = 'none';
        arrow_l.style.display = 'none';
        timer = setInterval(function () {
            arrow_r.click();
        }, 2000);
    })
    var num = 0;
    var circle = 0;

    // 根据图片数量生成相对应的小圆圈
    for (var i = 0; i < ul.children.length; i++) {
        var li = document.createElement('li');
        li.setAttribute('index', i);
        ol.appendChild(li);


        li.addEventListener('click', function () {
            for (var i = 0; i < ol.children.length; i++) {
                ol.children[i].className = '';
            }
            this.className = 'current';
            var n = this.getAttribute('index');
            num = n;
            circle = n;
            animate(ul, -n * carcouselWidth);
            console.log(n);
        })
    }

    ol.children[0].className = 'current';
    var first = ul.children[0].cloneNode(true);
    ul.appendChild(first);

    var flag = true;


    /* function circleChange() {
        for (var i = 0; i < ol.children.length; i++) {
            ol.children[i].className = '';
        }
        ol.children[circle].className = 'current';
    } */


    arrow_r.addEventListener('click', function () {

        if (flag) {
            flag = false;
            if (num == ul.children.length - 1) {
                ul.style.left = 0;
                num = 0;
            }
            num++;
            animate(ul, -num * carcouselWidth, function () {
                flag = true;
            });
        }

        circle++;
        if (circle == ol.children.length) {
            circle = 0;
        }

        circleChange();
    })

    arrow_l.addEventListener('click', function () {
        if (flag) {
            flag = false;
            if (num == 0) {
                num = ul.children.length - 1;
                ul.style.left = -num * carcouselWidth + 'px';

            }
            num--;
            animate(ul, -num * carcouselWidth, function () {
                flag = true;
            });

            circle--;
            circle = circle < 0 ? ol.children.length - 1 : circle;
            // 调用函数
            circleChange();
        }
    });


    function circleChange() {

        for (var i = 0; i < ol.children.length; i++) {
            ol.children[i].className = '';
        }

        ol.children[circle].className = 'current';
    }

    var timer = setInterval(function () {

        arrow_r.click();
    }, 2000);