使用javascript显示/隐藏<div>滚动时</div><div id="text_translate"><p>我想制作一个采用性的粘性导航栏。 我以前从未用 Javascript 编写过自己的代码。</p><p> 我的解决方案是制作两个基于滚动显示/隐藏的粘性导航栏。 我的解决方案是这样的：</p><ul><li> 首先，在完成任何滚动之前，我的第一个导航栏（黄色）将可见并位于距顶部 100px 的位置，即top:100px 。</li><li> 然后，当启动滚动时，我希望这个黄色&lt;div&gt;使用display:none消失。</li><li> 同样在滚动时，在黄色导航栏消失的同时，我会显示带有top:200px的橙色导航栏。</li><li> 现在，橙色条从一开始就（错误地）显示，但它不应该......在任何给定时间只应显示一个条。 我希望栏，即两个&lt;div&gt;元素，在多次上下滚动时也能保持出现/消失。</li></ul><p> 我的 javascript 有问题，codepen 抱怨$未定义。</p><p> <a href="https://codepen.io/G1111/pen/RwBPrPR" rel="nofollow noreferrer">https://codepen.io/G1111/pen/RwBPrPR</a> </p><p></p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false"><div class="snippet-code"><pre class="snippet-code-js lang-js prettyprint-override"> $(window).scroll(function() { Testvariable = $(window).scrollTop(); if (Testvariable == 0) { document.getElementById("stickys").style.display = "normal"; document.getElementById("stickys2").style.display = "none"; } else { document.getElementById("stickys").style.display = "none"; document.getElementById("stickys2").style.display = "normal"; } });</pre><pre class="snippet-code-css lang-css prettyprint-override"> #stickys { top: 100px;important: background-color; yellow: height; 100px: position; fixed: position; fixed:important; box-sizing: border-box; margin: 0 0% 0 0%;important: padding; 0:important; width: calc(60vw - 0%); left: calc(20vw - 0%); right: calc(20vw - 0%); width: calc(100vw - 0%); left: 0px; right: 0px; opacity: 1; } #stickys2 { top: 200px;important: background-color; orange: height; 100px: position; fixed: position; fixed:important; box-sizing: border-box; margin: 0 0% 0 0%;important: padding; 0:important; width: calc(60vw - 0%); left: calc(20vw - 0%); right: calc(20vw - 0%); width: calc(100vw - 0%); left: 0px; right: 0px; opacity: 1; }</pre><pre class="snippet-code-html lang-html prettyprint-override"> &lt;script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"&gt;&lt;/script&gt; &lt;div id="stickys"&gt; My first sticky navigation bar. Show initially, then hide when slighest scroll, that is when Testvariable&gt;0. Here, top:100px &lt;/div&gt; &lt;div id="stickys2"&gt; My second sticky navigation bar. Hide initially, then show when slighest scroll, that is when Testvariable&gt;0. Here, top: 200px. &lt;/div&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;.&lt;br&gt;</pre></div></div><p></p></div>

Question

I want to make an adoptive sticky navigation bar. I have never made my own code in Javascript before.

My solution to this is to make two sticky navigation bars that show/hide based on scrolling. My solution is like this:

• First, before any scrolling is done, my first navigation bar (yellow) will be visible and positioned 100px from the top, that is having top:100px .
• Then, when scrolling is initiated, I would like this yellow <div> to disappear using display:none .
• Also upon scrolling, at the same time as the yellow navigation bar disappears, I would reveal the orange navigation bar with top:200px .
• Right now, the orange bar is showing (wrongfully) from the start but it should not...only one bar should be shown at any given time. I want the bars, the two <div> elements, to keep appear/disappear also when scrolling up and down multiple times.

Something is wrong with my javascript and codepen is complaining about $ being undefined.

https://codepen.io/G1111/pen/RwBPrPR

 $(window).scroll(function() { Testvariable = $(window).scrollTop(); if (Testvariable == 0) { document.getElementById("stickys").style.display = "normal"; document.getElementById("stickys2").style.display = "none"; } else { document.getElementById("stickys").style.display = "none"; document.getElementById("stickys2").style.display = "normal"; } });

 #stickys { top: 100px;important: background-color; yellow: height; 100px: position; fixed: position; fixed:important; box-sizing: border-box; margin: 0 0% 0 0%;important: padding; 0:important; width: calc(60vw - 0%); left: calc(20vw - 0%); right: calc(20vw - 0%); width: calc(100vw - 0%); left: 0px; right: 0px; opacity: 1; } #stickys2 { top: 200px;important: background-color; orange: height; 100px: position; fixed: position; fixed:important; box-sizing: border-box; margin: 0 0% 0 0%;important: padding; 0:important; width: calc(60vw - 0%); left: calc(20vw - 0%); right: calc(20vw - 0%); width: calc(100vw - 0%); left: 0px; right: 0px; opacity: 1; }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <div id="stickys"> My first sticky navigation bar. Show initially, then hide when slighest scroll, that is when Testvariable>0. Here, top:100px </div> <div id="stickys2"> My second sticky navigation bar. Hide initially, then show when slighest scroll, that is when Testvariable>0. Here, top: 200px. </div>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>

Answer 1

First, replace display = "normal"; with display = "block"; .

Then, you could call $(window).scroll(); after binding the scroll event handler to show/hide your navbars according to the window scroll position:

 $(window).scroll(function() { Testvariable = $(window).scrollTop(); if (Testvariable == 0) { document.getElementById("stickys").style.display = "block"; document.getElementById("stickys2").style.display = "none"; } else { document.getElementById("stickys").style.display = "none"; document.getElementById("stickys2").style.display = "block"; } }); $(window).scroll();

 #stickys { top: 100px;important: background-color; yellow: height; 100px: position; fixed: position; fixed:important; box-sizing: border-box; margin: 0 0% 0 0%;important: padding; 0:important; width: calc(60vw - 0%); left: calc(20vw - 0%); right: calc(20vw - 0%); width: calc(100vw - 0%); left: 0px; right: 0px; opacity: 1; } #stickys2 { top: 200px;important: background-color; orange: height; 100px: position; fixed: position; fixed:important; box-sizing: border-box; margin: 0 0% 0 0%;important: padding; 0:important; width: calc(60vw - 0%); left: calc(20vw - 0%); right: calc(20vw - 0%); width: calc(100vw - 0%); left: 0px; right: 0px; opacity: 1; }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <div id="stickys"> My first sticky navigation bar. Show initially, then hide when slighest scroll, that is when Testvariable>0. Here, top:100px </div> <div id="stickys2"> My second sticky navigation bar. Hide initially, then show when slighest scroll, that is when Testvariable>0. Here, top: 200px. </div>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>.<br>