如何获取滚动条内可见div的ID

Question

我在带滚动条的主div中没有​​几个div。在这里，我需要在单击按钮时获得滚动条中可见div的ID。我对此一无所知，有人可以帮我吗这是下面的代码。

html

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<p>Demonstrate fadeIn() with different parameters.</p>

<button>Click to get the current visible id</button><br>
<div id="mainbody">
<div id="div1">it is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).</div><br>
<div id="div2">it is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).</div><br>
<div id="div3">it is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).</div>
</div>

样式

#mainbody{
height:70px;
overflow:auto;
}

脚本

$(document).ready(function(){
    $("button").click(function(){

    });
});

Answer 1

$("button").click(function(){
      $("#mainbody").find("div:visible").each(function(){
            alert($(this).attr('id'));
      });
});

示例：

$(document).ready(function(){

    $("button").click(function(){
        $("#mainbody").find("div:visible").each(function(){
     		    alert($(this).attr('id'));
        });
    });
 
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<p>Demonstrate fadeIn() with different parameters.</p>

<button>Click to get the current visible id</button><br>
<div id="mainbody">
<div id="div1">it is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).</div><br>
<div id="div2">it is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).</div><br>
<div id="div3">it is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).</div>
</div>

Answer 2

$(document).ready(function(){

const main = document.getElementById('mainbody')
const elementHeight = main.scrollHeight/3;

    $("button").click(function(){

            console.log(Math.floor(main.scrollTop / elementHeight) + 1)
    });
});

这是工作示例： https://jsfiddle.net/bj1a8ksr/