Seamless scrolling plugin based on writing jQuery

Seamless scrolling plugin based on writing jQuery_jquery

WBOY

Release： 2016-05-16 16:40:33

Original

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First let’s look at the html skeleton, as follows:

<div class="box">
    <ul>
      <li>111</li>
      <li>222</li>
      <li>333</li>
    </ul>
</div>

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The structure is simple and clear, nothing much to say.

Let’s talk about the implementation principle:
The div box is the outermost box. Give it a specified width and height. Remember to add an overflow:hidden (hidden content beyond) style to the box, because scrolling will definitely exceed the box.
We use js to control the margin of the ul tag to achieve scrolling. Horizontal scrolling controls margin-left; vertical scrolling controls margin-top;
In the initial state, we also need to make conditional judgments to determine whether to scroll. That is: when the length of ul is less than the length of the outer box, no scrolling is performed, otherwise, scrolling is performed.
The length of ul is calculated, that is: the length of a single li in ul multiplied by the number of li's. ul_width = li_width * li_num;
The reason why seamless scrolling can be achieved is that every time the length of the scroll is just larger than the length of a single li, we move the first li of ul to the end of ul, and the cycle starts again and again, infinitely (about this
One thing, you can check it without setting overflow:hidden first).

Telling a principle is a test of my ability to express myself. I hope I explained it clearly.

Let’s look at the plug-in’s implementation code:

(function ($) {
  $.fn.Scroll = function (options) {
    //将当前上下文对象存入root
    var root = this;

    //默认配置
    var settings = {
      speed: 40,   //滚动速度,值越大速度越慢
      direction: "x" //滚动方向("x"或者"y" [x横向;y纵向])
    };

    //不为空，则合并参数
    if (options)
      $.extend(settings, options);


    var timer = [];   //计时器
    var marquee;    //滚动器(函数)
    var isRoll;     //判断是否滚动(函数)

    var _ul = $("> ul", root);     //ul标签
    var _li = $("> ul > li", root);   //li标签(集合)

    var li_num = _li.length;  //li标签个数
    var li_first = _li.first();  //获取单个li标签


    //判断为纵向还是横向，并进行相应操作
    if (settings.direction == "x") {
　　　　　　　
　　　　　　 var li_w = li_first.outerWidth(true); //单个li标签的宽度
　　　　　　 var ul_w = li_w * li_num; 　　　　　　 //ul标签的宽度

      _ul.css({ width: ul_w }); //设置ul宽度

      marquee = function () {
        _ul.animate({ marginLeft: "-=1" }, 0, function () {
          var _mleft = Math.abs(parseInt($(this).css("margin-left")));
          if (_mleft > li_w) { //滚动长度一旦大于单个li的长度
            $("> li:first", $(this)).appendTo($(this)); //就把第一个li移到最后
            $(this).css("margin-left", 0); //滚动长度归0
          }
        });
      };
      //ul长度小于box长度时则不滚动，反之滚动
      isRoll = function (t) {
        if (ul_w <= root.width())
          clearInterval(t);
        else
          marquee();
      }
    }
    else {
　　　　　　 var li_h = li_first.outerHeight(true); //单个li标签的高度 
　　　　　　 var ul_h = li_h * li_num; //ul标签的高度

      _ul.css({ height: ul_h }); //设置ul高度

      marquee = function () {
        _ul.animate({ marginTop: "-=1" }, 0, function () {
          var _mtop = Math.abs(parseInt($(this).css("margin-top"))); //取绝对值
          if (_mtop > li_h) { 
            $("> li:first", $(this)).appendTo($(this));
            $(this).css("margin-top", 0);
          }
        });
      };
      //ul长度小于box长度时则不滚动，反之滚动
      isRoll = function (t) {
        if (ul_h <= root.height())
          clearInterval(t);
        else
          marquee();
      }
    }

    //遵循链式原则，并进行初始化
    return root.each(function (i) {
      //超出内容隐藏，防止用户没写overflow样式
      $(this).css({ overflow: "hidden" });

      timer[i] = setInterval(function () {
        isRoll(timer[i]);
      }, settings.speed);

      //鼠标进入停止滚动，离开继续滚动
      $(this).hover(function () {
        clearInterval(timer[i]);
      }, function () {
        timer[i] = setInterval(function () {
          isRoll(timer[i]);
        }, settings.speed);
      });

    });

  };
})(jQuery);

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The basic code description comments are written very clearly. The following is an explanation of individual knowledge points:

1.) var timer=[]; The timer was not declared as an array type before. When I was writing the demo, because there were two seamless scrolling applications on the page at the same time (to demonstrate horizontal and vertical), it appeared Bug.

Because the two of them share a timer, when the mouse enters one of them, the timer of the other one is also cleared. Then modify the code to declare it as an array object, and then use root.each() to implement
Now each plug-in application has its own independent timer and does not interfere with each other. In other words, this plug-in supports multiple seamless scrolling applications on the page at the same time.

2.) outerWidth() /outerHeight() function. This function is more powerful, it gets more than just the width/height of the element,

Actually outerWidth()=width borderLeft borderRight marginLeft marinRight;
When it is set to true, that is: outerWidth(true), it will also calculate padding:
outerWidth()=width borderLeft borderRight marginLeft marinRight paddingLeft paddingRight;

How about it, isn’t it very powerful!

The DEMO code is given below:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<style type="text/css">
  *{ margin:0; padding:0;}
  ul,ul li{ list-style:none;}  
  .wrap{ width:1000px; margin:50px auto;}  
  .box1,.box2,.box3{ overflow:hidden; float:left;border:1px solid gray;}  
  .box1{ width:200px; height:450px;}
  .box1 ul li{ width:200px; height:100px;} 
  .box2,.box3{ width:450px;height:150px; margin:40px;}
  .box2 ul li,.box3 ul li{ width:100px; height:150px; float:left;}
  
</style>
</head>

<body>
<div class="wrap">

  <div class="box1">
    <ul>
      <li>111纵向</li>
      <li>222纵向</li>
      <li>333纵向</li>
      <li>444纵向</li>
      <li>555纵向</li>
      <li>666纵向</li>
    </ul>
  </div>

  <div class="box2">
    <ul>
      <li>111横向</li>
      <li>222横向</li>
      <li>333横向</li>
      <li>444横向</li>
      <li>555横向</li>
      <li>666横向</li>
    </ul>
  </div> 
  
  <div class="box3">  
    <ul>
      <li>ul长度小于box长度，不滚动</li>
      <li>222横向</li>
      <li>333横向</li>      
    </ul>
  </div>  
</div>

<script type="text/javascript" src="js/jquery.js"></script>
<script type="text/javascript" src="js/jquery.similar.scroll.js"></script>
<script type="text/javascript">
  $(function () {
    //奇数背景设置为灰色
    $('.box1 li:even,.box2 li:even,.box3 li:even').css({ backgroundColor: "gray" });

    $(".box1").Scroll({ direction: "y" }); //设置为纵向滚动
    $(".box2").Scroll(); //默认横向滚动
    $(".box3").Scroll();
  });
</script>
</body>
</html>

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Effect picture: