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

The content of this article is about using timers to achieve seamless scrolling effects in js (code implementation). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

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  alt="js uses timer to achieve seamless scrolling effect (code implementation)" ></li>
      <li><img  alt="js uses timer to achieve seamless scrolling effect (code implementation)" ></li>
      <li><img  alt="js uses timer to achieve seamless scrolling effect (code implementation)" ></li>
      <li><img  alt="js uses timer to achieve seamless scrolling effect (code implementation)" ></li>
    </ul>
  </div>

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