图片轮播

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
        <style>
            *{
                margin: 0px;
                padding: 0px;
            }
            #stage{
                 300px;
                height: 200px;
                border: 10px solid black;
                margin: 300px;
                position: relative;
                overflow: hidden;
            }
            #ad-banner{
                 1500px;
                height: 200px;
                background-color: brown;
                position: relative;
                z-index: 980;
                /*margin-left: -300px;*/
            }
            .ad{
                position: relative;
                 300px;
                height: 200px;
                float: left;
                color: white;
                font-size: 100px;
                text-align: center;
                line-height: 200px;
                z-index: 990;
            }
            #btn-left,#btn-right{
                 20px;
                height: 30px;
                position: absolute;
                top: 85px;
                background-color: black;
                z-index: 999;
                color: white;
                opacity: 0.5;
                text-align: center;
                line-height: 30px;
                font-size: 15px;
                font-weight: bold;
            }
            #btn-left{
                left: 0px;
            }
            #btn-right{
                right: 0px;
            }
            
            #btn-left:hover,#btn-right:hover{
                opacity: 0.8;
                cursor: pointer;
            }
        </style>
    </head>
    <body>
        <div id="stage">
            
            <div id="btn-right" onclick="moveLeftclick()">></div>
            <div id="btn-left" onclick="moveRightclick()"><</div>
            <div id="ad-banner">
                <div class="ad" style="background-color: hotpink;">1</div>
                <div class="ad" style="background-color: darkcyan">2</div>
                <div class="ad" style="background-color: coral">3</div>
                <div class="ad" style="background-color: #4CAE4C">4</div>
                <div class="ad" style="background-color: blueviolet">5</div>
            </div>
        </div>
    </body>
</html>
<script>
    var ad_banner = document.getElementById("ad-banner");
    var arr = [];
    var count = 1;
    function moveLeftclick(){
        if(count == 5){
            return false;
        }else{
            arr.push(window.setInterval("moveLeft()",20));
        }
    }
    
    function moveLeft(){
        ad_banner.style.marginLeft = ad_banner.offsetLeft - 10 + "px";
        if(ad_banner.offsetLeft == -300 * count)
        {
            for(var x in arr){
                window.clearInterval(arr[x]);
            }
            count++;
        }
    }
    function moveRightclick() {
        if (count == 1) {
            return false;
        } else {
            arr.push(window.setInterval(moveRight, 20));
        }

    }

    function moveRight() {
        ad_banner.style.marginLeft = ad_banner.offsetLeft + 10 + "px";
        if (ad_banner.offsetLeft == -300 * (count - 2)) {
            for (var x in arr) {
                window.clearInterval(arr[x]);
            }
            count--;
        }

    }

    
    window.setInterval("moveLeftclick()",5000);
</script>