ScrollingTop卡住了

Question

下面的代码向下滚动就好了但不是顶部。当它到达底部或顶部时会卡住。但如果不是如此接近底部和顶部它工作正常。 看起来如果你点击底部丰富的时间，你必须点击相同的数字才能滚动到顶部。

有任何线索吗？

＆＃13;

＆＃13;

var scrolled = 0;

$(function () {
     
     

    $("#upClick").on("click", function () {
        console.log("upClick");
        scrolled = scrolled - 100;
        $(".nav").animate({
            scrollTop: scrolled
        });
    });

    $("#downClick").on("click", function () {
        console.log("downClick");
        scrolled = scrolled + 100;
        $(".nav").animate({
            scrollTop: scrolled
        });
    });
});

＆＃13;

.arrow-button {
    cursor: pointer;
}

.arrow-button:hover {
    position: relative;
    top: 1px;
    left: 1px;
    border-color: #e5e5e5;
    cursor: pointer;
}

#sidebar {
    width: 880px;
    font-weight: bold;
  
}

.nav {
    max-height: 150px;
    overflow-y:hidden;
}

＆＃13;

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="row second-row">
        <div class="col-md-11">
            <div   id="sidebar" role="navigation" style="float:left">
                <div class="well sidebar-nav">
                    <ul class="nav">
                        <li class="active"><a href="#">Maths</a></li>
                        <li><a href="#">English</a></li>
                        <li><a href="#">Art and Design</a></li>
                        <li><a href="#">Drama</a></li>
                        <li><a href="#">Music</a></li>
                        <li><a href="#">Physics</a></li>
                        <li><a href="#">Chemistry</a></li>
                        <li><a href="#">Biology</a></li>
                        <li><a href="#">Home economics</a></li>
                        <li><a href="#">Physical Education</a></li>
                        <li><a href="#">Computing Science</a></li>
                        <li><a href="#">French</a></li>
                        <li><a href="#">German</a></li>
                        <li><a href="#">Mandarin</a></li>
                        <li><a href="#">Religious Education</a></li>
                        <li><a href="#">Modern Studies</a></li>
                        <li><a href="#">Geography</a></li>
                        <li><a href="#">History</a></li>
                        <li><a href="#">Creative computing</a></li>
                        <li><a href="#">Craft, Design and Technology</a></li>
                    </ul>
                </div><!--/.well -->
            </div>
        </div>
        <div class="col-md-1" style="padding-left:35px;">
            <img src="images/arrow-up.png" width="70" class="arrow-button" id="upClick" />
            <img src="images/arrow-down.png" width="70" style="margin-top:50px;" class="arrow-button" id="downClick" />
        </div>
    </div>

＆＃13;

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Answer 1

好吧......好吧：3 小提示：

• .stop（）播放另一个动画。
• 检查滚动的最大值和最小值

var scrolled = 0;

    $(function () {

          $("#upClick").on("click", function () {
            console.log("upClick");
            scrolled = scrolled - 100;
            
            if(scrolled < 0) scrolled = 0;
            
            $(".nav").stop().animate({
                scrollTop: scrolled
            });
        });

        $("#downClick").on("click", function () {
            console.log("downClick");
            scrolled = scrolled + 100;
            
            if(scrolled > $(".nav").prop("scrollHeight"))
            	scrolled = $(".nav").prop("scrollHeight");
            
            $(".nav").stop().animate({
                scrollTop: scrolled
            });
        });
    });

.nav {
    max-height: 150px;
    overflow-y: auto;
}

  
      <link rel="stylesheet" type="text/css" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
      <script type="text/javascript" src="https://code.jquery.com/jquery-2.2.3.min.js"></script>
      <script type="text/javascript" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>


<div class="row second-row">
        <div class="col-md-11">
            <div id="sidebar" role="navigation"  >
                <div class="well sidebar-nav">
                    <ul class="nav">
                        <li class="active"><a href="#">Maths</a></li>
                        <li><a href="#">English</a></li>
                        <li><a href="#">Art and Design</a></li>
                        <li><a href="#">Drama</a></li>
                        <li><a href="#">Music</a></li>
                        <li><a href="#">Physics</a></li>
                        <li><a href="#">Chemistry</a></li>                   
                        <li><a href="#">Modern Studies</a></li>
                        <li><a href="#">Geography</a></li>
                        <li><a href="#">History</a></li>
                        <li><a href="#">Creative computing</a></li>
                        <li><a href="#">Craft, Design and Technology</a></li>
                    </ul>
                </div> 
            </div>
        </div>
        <div class="col-md-1" >
            <img src="images/arrow-up.png" width="70" class="arrow-button" id="upClick" />
            <img src="images/arrow-down.png" width="70"   class="arrow-button" id="downClick" />
        </div>
    </div>

Answer 2

当您尝试滚动时，请始终记住它不应该为负值。

在程序开始时，它会进入-ve值，添加条件

 $("#upClick").on("click", function () {
        console.log("upClick");
        scrolled = scrolled - 100;
        if(scrolled>0){
      $(".nav").animate({
            scrollTop: scrolled
        });  
      }
    });