news.html

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>加载更多</title>
  <style type="text/css">

    ul,li {
      list-style: none;
      padding: 0;
    }
    a {
      text-decoration: none;
    }
    li {
     display: block;
     margin: 10px auto;
     border: 1px solid #ccc;
     padding: 5px;
     text-align: center;
     /*
     width: 600px;
     height: 30px;
     box-sizing: border-box;
     */
    }
    .ct li:hover {
      background-color: green;
      cursor: pointer;
    }
    .btn {
      visibility: hidden;
    }
/*    .btn {
      cursor: pointer;
      width: 100px;
      height: 40px;
      border-radius: 3px;
      font-size: 16px;
      margin: 20px auto;
      display: block;
      outline: none;
    }
    .btn:hover {
      background-color: pink;
      color: green;
    }*/
  </style>
</head>
<body>
  <ul class="ct"></ul>
  <button class="btn">加载更多</button>
  <script src='jquery/jquery-3.2.1.min.js'></script>
  <script type="text/javascript">
    var $ct = $('.ct')
    var isOver = false
    var lock = true
    var index = 0
    getNews()
    
    $(window).on('scroll',check)

      // check()
      // if (!lock) {
      //   return
      // }      
      // if (isVisible($('.btn'))&&!isOver&&lock) {
      //   getNews()
      //   console.log('a')
      // }
      // lock = false
    // })
      
    function getNews(){
      lock = false
      $.ajax({
      url:'/loadMore',
      type:'get',
      dataType:'json',
      data:{
        index:index,
        length:3
      },
      success:function(ret){
        lock = true
        if (ret.status == '0') {
          // index++
          appendHtml(ret.data)
          console.log('1') 
          check()
          
          // if (isVisible($('.btn'))&&!isOver&&lock) {
          //   getNews()
          //   console.log('a')
          // }
          
        } else {
          console.log('2')
        }
        // lock = true
        },
        error:function(){
          console.log('出错了')
        }, 
      })
    }
    function check(){
      if (isVisible($('.btn'))&&!isOver&&lock) {
        getNews()
        console.log('a')
      }
    }
    function appendHtml(news){
      if (news.length === 0) {
        $ct.append('<p>没有更多数据了</p>')
        isOver = true
        console.log('b')
      } 
      var htmls = ''
      $.each(news,function(idx,prod){
        htmls ='<li><a href="#">'+prod+'</a></li>'
        $ct.append(htmls)
        index++
      })
      // $ct.append(htmls)
    }
    function isVisible($node){
      var windowHeight = $(window).height()
      var offsetTop = $node.offset().top
      var scrollTop = $(window).scrollTop()
      var nodeHeight = $node.outerHeight(true)
      if (scrollTop<offsetTop+nodeHeight&&scrollTop>offsetTop-windowHeight) {
        return true
      } else {
        return false
      }
    }

  </script>
</body>
</html>