js实现幻灯片

使用原生js实现轮播图

html代码

    <div class="slide">
        <ul>
            <li style="display: block;">
                <img src="1.jpg">
            </li>
            <li>
                <img src="2.jpg">
            </li>
            <li>
                <img src="3.jpg">
            </li>
            <li>
                <img src="4.jpg">
            </li>
            <li>
                <img src="5.jpg">
            </li>
        </ul>
        <span class="pre"> < </span>
        <span class="next"> > </span>
    </div>

css代码

*{padding:0; margin: 0;}
ul,ol,li{list-style: none;}
img{vertical-align: top; border: none;}
a{text-decoration: none;}
body{font-size: 14px; font-family: '微软雅黑';}


.slide{
    width: 250px;
    height: 90px;
    margin: 100px auto;
    position: relative;
}
.slide>ul>li{
    position: absolute;
    float: left;
    display: none;
}
.slide>ul>li:first-child{
    display:block;
}
.slide>ul>li>img{
    width:250px; height:90px;
}

.slide>span{
    position:absolute;
    top:30px;
    background-color: rgba(0, 0, 0, 0.3);
    color: #fff;
    display:block;
    width: 20px; text-align: center;
    height:30px; line-height: 30px;
}
.slide>.pre{
    left:0;
    border-top-right-radius: 3px;
    border-bottom-right-radius: 3px;
}
.slide>.next{
    right: 0;
    border-top-left-radius: 3px;
    border-bottom-left-radius: 3px;
}

js代码

        let index = 0; //当前索引
        var pre = document.getElementsByClassName("pre")[0];
        var next = document.getElementsByClassName("next")[0];
        var lis = document.getElementsByClassName("slide")[0].children[0].children;
        next.onclick = function() {
            index++;
            for (let i = 0; i < lis.length; i++) {
                lis[i].style.display = "none";
            }
            // index = index + 1 == lis.length ? 0 : index;最后一张则回到第一张
            if (index == lis.length) {
                index = 0;
            }
            lis[index].style.display = "block";

        }
        pre.onclick = function() {
            index--;
            for (let i = 0; i < lis.length; i++) {
                lis[i].style.display = "none";
            }
            // index = index + 1 == lis.length ? 0 : index;第一张上一张则为最后一张
            if (index < 0) {
                index = lis.length - 1;
            }
            lis[index].style.display = "block";
        }

        function auto() {
            next.click();
        }
        let s = setInterval("auto()", 2000);
        for (let i = 0; i < lis.length; i++) {
            lis[i].onmouseenter = function() {
                clearInterval(s);
            }
            lis[i].onmouseleave = function() {
                s = setInterval("auto()", 2000);
            }

        }