原生js写星星

    <style>
        *{
            margin: 0;
            padding: 0;
        }
        ul li{
            list-style: none;
        }
        ul{
            margin: 100px 0 0 300px;
            display: inline-block;
        }
        .star li{
            width: 40px;
            height: 40px;
            background: url("../assents/[email protected]");
            float: left;
        }
        .star li.active{
            width: 40px;
            height: 40px;
            background: url("../assents/[email protected]");
        }
    </style>

 <ul class="star">
        <li></li>
        <li></li>
        <li></li>
        <li></li>
        <li></li>
    </ul>

<script>
    var li = document.querySelectorAll('.star li')
    var star = document.querySelector('.star')

    var curIndex = null

    //1,
    for(var i = 0;i<li.length;i++){
        li[i].setAttribute('data-idx',i)
        //知道经过的元素
        li[i].onmouseenter = function () {
            //获取下标
            var idx = this.getAttribute('data-idx')
            show(idx)
        }
        li[i].onclick = function () {
            var idx = this.getAttribute('data-idx')
            curIndex = idx
            console.log(idx)
            show(curIndex)
        }
    }

    //2,
    function show(num) {
        //首先让他们都暂时不亮
        for(var j = 0;j<li.length;j++){
            li[j].className = ''
        }
        //移到哪里亮到哪儿
        for(var i = 0;i<=num;i++){
            li[i].className = 'active'
        }
    }

    //3,
    //鼠标离开时判断有没有点击
    star.onmouseleave = function () {
        if(curIndex == null){
            for(var j = 0;j<li.length;j++){
                li[j].className = ''
            }
        }else{
            for(var i = 0;i<li.length;i++){
                li[i].className = ''
            }
            for(var j = 0;j<=curIndex;j++){
                li[j].className = 'active'
            }
        }
    }
    star.onmouseenter =function () {
        for(var j = 0;j<li.length;j++){
            li[j].className = ''
            if(curIndex !== null){
                for(var k = 0;k<=curIndex;k++){
                    li[k].className = 'active'
                }
            }
        }
    }

</script>