js uses timer to achieve seamless scrolling effect (code implementation)

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I recently learned about timers and organized timers to achieve seamless scrolling.

Principle

• #Use a timer to implement ul scrolling.

• When scrolling exceeds half of the total length of ul (i.e. oUl.offsetLeft

• When the left distance of ul is greater than 0, switch left to the normal length of the total length (i.e. oUl.style.left=-oUl.offsetWidth/2 "px").

• When scrolling to the left-2

• When scrolling to the right 2

Code implementation

nbsp;html>


  <meta>
  <title>定时器实现无缝滚动例子</title>

<style>
  * {
    margin: 0;
    padding: 0;
  }
  #div1 {
    width: 700px;/* 按照显示四张图片计算宽度 */
    height: 117px;
    margin: 20px auto;/* 页面居中 */
    position: relative;
    overflow: hidden;/* 超出部分隐藏 */
  }
  #div1 ul{
    position: absolute;
    left: 0;
    top: 0;
  }
  #div1 ul li{
    float: left;
    width: 175px;
    height: 117px;
    list-style-type: none;
  }
</style>
<script>
  window.onload=function(){
    var oDiv=document.getElementById("div1");//获取div1元素
    var oUl=oDiv.getElementsByTagName("ul")[0];//获取ul元素
    var oLi=oUl.getElementsByTagName("li");//获取li元素
    var oLeft=document.getElementById("moveleft");//获取向左滚动元素
    var oRight=document.getElementById("moveright");//获取向右滚动元素
    oUl.innerHTML+=oUl.innerHTML;//把ul中li元素重复拼接一次
    var speed=-2;//设置左滚动和右滚动，如果为负值为左滚动正值为右滚动
    oUl.style.width=oLi[0].offsetWidth*oLi.length+"px";//设置ul宽度为li宽度总和
    function move(){//定时器中的方法独立出来
      if(oUl.offsetLeft<-oUl.offsetWidth/2){//左移，当ul左侧的距离小于总距离的一半时就把ul的left设置为0，因为是负值所以加-
        oUl.style.left="0";
      }
      if(oUl.offsetLeft>0){//右移，当ul左侧的距离大于0时，把ul的left设置为ul总宽度的一半，加-
        oUl.style.left=-oUl.offsetWidth/2+"px";
      }
      oUl.style.left=oUl.offsetLeft+speed+"px";//不符合上述两个要求的时候就直接滚动
    }
    var timer=setInterval(move,30);//设置定时器

    oDiv.onmouseover=function(){//当鼠标划到div1时清除定时器
      clearInterval(timer);
    }
    oDiv.onmouseout=function(){//当鼠标移除div1时重新开启定时器
      timer=setInterval(move,30);
    }

    oLeft.onclick=function(){//当点击向左滚动按钮时，设置为2
      speed=-2;
    }

    oRight.onclick=function(){//当点击向右滚动按钮时，设置为-2
      speed=2;
    }
  }
</script>

  <a>向左滚动</a>
  <a>向右滚动</a>
  <div>
    <ul>
      <li><img  src="/static/imghw/default1.png" data-src="img/1.jpg" class="lazy" alt="js uses timer to achieve seamless scrolling effect (code implementation)" ></li>
      <li><img  src="/static/imghw/default1.png" data-src="img/2.jpg" class="lazy" alt="js uses timer to achieve seamless scrolling effect (code implementation)" ></li>
      <li><img  src="/static/imghw/default1.png" data-src="img/3.jpg" class="lazy" alt="js uses timer to achieve seamless scrolling effect (code implementation)" ></li>
      <li><img  src="/static/imghw/default1.png" data-src="img/4.jpg" class="lazy" alt="js uses timer to achieve seamless scrolling effect (code implementation)" ></li>
    </ul>
  </div>

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