我有一個網頁,我需要獲取我的頁面元素的當前頂部位置.

我有一些div,他們每個都有100％的高度,我有我的內容.

我希望從頂部獲得這些div的位置并使用它.但是當我這樣做時,它只返回一個數字,并且在滾動時不會改變.

這是我的代碼：

HTML：

<header id="header">
   <div id="menu-div" class="container-full">
        <div class="container">
            <a href="#">TEST</a>
            <a href="#">TEST</a>
            <a href="#">Test</a>
            <a href="#">Test</a>
            <a href="#">Test</a>
            <a id="request-demo-a" class="pull-right" href="#">TEST demo</a>
            </div>
        </div>
   </header>


   <div id="first-div" class="center a-div">
   test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>
   </div>


   <div id="full-div" class="container a-div">

        test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>test content here...<br/>
        </div>

  <div id="other-div" class=" a-div">
  <br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/>

  </div>



  <div id="other-div" class=" a-div">
  <br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/><br/>test content here...<br/>test content here...<br/>test content here...<br/>

  </div>

CSS：

.a-div{
    height:100%;
}


#full-div{
    position:absolute;
    top:100%;
    width: 100%;
    height: auto;
    background: white;
    z-index:5;

}


#first-div{
    width:100%;
    height:100%;
    position:fixed;
    left:0;
    right:0;
    top:0;
    bottom: 0;
    margin: auto;
    color:white;
    z-index:-1;


}
#menu-div{
    background: white;
    padding:7px;
    position: fixed;
    z-index:10;
}


#menu-div .container a{
    margin-left: 15px;
    display:inline-block;
    font-size:large;
}

#request-demo-a{
    padding:5px;
    border: 2px solid #FF8000;
    color: white;
    text-shadow: none;
    background: orange;
    text-decoration: navajowhite;
}

#request-demo-a:hover, #request-demo-a:focus{
    background: #FF8000;
}

JavaScript(Jquery)：

$(function(){
        /**start:Scroll*/
        $(document).scroll(function(){
         $("#request-demo-a").html($('#full-div').offset().top);
         /// I want this return current value of full-div!
         //And when it become equel 0 do something! (This is just example)

        });
        /**End: Scroll*/      
})

JSFiddle-Demo

我想獲得#full-div的位置并使用它,當它變?yōu)榈扔?時,做某事(意味著當到達頂部時)和其他div(s)我想在某個位置做某事.

但為什么$(‘#full-div’).offset().top只是在滾動時返回一個數字？

解決方法:

偏移量在滾動時不會改變,offset()檢索元素相對于文檔的當前位置,并且整個文檔都在滾動,因此沒有真正改變,元素仍然在文檔內的完全相同的位置.

如果要滾動距離,請使用scrollTop,然后將其與元素偏移進行比較,以查看頁面是否滾動的元素量與元素到文檔頂部的距離相同

$(document).on('scroll', function(){

    var scrolled = $(window).scrollTop();
    var offset   = $('#full-div').offset().top;

    if ( offset <= scrolled ) {
       // element is scrolled to top or above
    }

});