HTML中的TAB:默认选择第一个TAB

TABS in HTML: Select first TAB by default

本文关键字：TAB 选择 第一个 默认 中的 HTML      更新时间：2023-09-26

我在HTML中尝试TABBING。我正在使用W3SCHOOLS的教程。

下面是源代码。它工作得很好，但我面临的问题是默认选择第一个选项卡，这在本教程中是缺失的。我希望第一个选项卡应该自动选择时，页面加载和内容应该自动显示。

<!DOCTYPE html>
<html>
<style>
body {font-family: "Lato", sans-serif;}
ul.tab {
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    border: 1px solid #ccc;
    background-color: #f1f1f1;
}
/* Float the list items side by side */
ul.tab li {float: left;}
/* Style the links inside the list items */
ul.tab li a {
    display: inline-block;
    color: black;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
    transition: 0.3s;
    font-size: 17px;
}
/* Change background color of links on hover */
ul.tab li a:hover {
    background-color: #ddd;
}
/* Create an active/current tablink class */
ul.tab li a:focus, .active {
    background-color: #ccc;
}
/* Style the tab content */
.tabcontent {
    display: none;
    padding: 6px 12px;
    -webkit-animation: fadeEffect 1s;
    animation: fadeEffect 1s;
}
@-webkit-keyframes fadeEffect {
    from {opacity: 0;}
    to {opacity: 1;}
}
@keyframes fadeEffect {
    from {opacity: 0;}
    to {opacity: 1;}
}
</style>
<body>
<h3>Fade in Tabs</h3>
<ul class="tab">
  <li><a href="#" class="tablinks" onclick="openCity(event, 'London')">London</a></li>
  <li><a href="#" class="tablinks" onclick="openCity(event, 'Paris')">Paris</a></li>
  <li><a href="#" class="tablinks" onclick="openCity(event, 'Tokyo')">Tokyo</a></li>
</ul>
<div id="London" class="tabcontent">
  <h3>London</h3>
  <p>London is the capital city of England.</p>
</div>
<div id="Paris" class="tabcontent">
  <h3>Paris</h3>
  <p>Paris is the capital of France.</p>
</div>
<div id="Tokyo" class="tabcontent">
  <h3>Tokyo</h3>
  <p>Tokyo is the capital of Japan.</p>
</div>
<script>
function openCity(evt, cityName) {
    var i, tabcontent, tablinks;
    tabcontent = document.getElementsByClassName("tabcontent");
    for (i = 0; i < tabcontent.length; i++) {
        tabcontent[i].style.display = "none";
    }
    tablinks = document.getElementsByClassName("tablinks");
    for (i = 0; i < tablinks.length; i++) {
        tablinks[i].className = tablinks[i].className.replace(" active", "");
    }
    document.getElementById(cityName).style.display = "block";
    evt.currentTarget.className += " active";
}
</script>
</body>
</html>

我应该在Javascript中做什么改变来默认选择第一个选项卡?我在for循环中尝试了以下行，但没有工作:

tablinks[0].className += " active";

在第一个LI的锚标记中添加class=active，并在下面的div中更新以下内容:

div id=London class=tabcontent style=display:block

这是一个工作的jsfield

这是一种纯粹的javascript方式，只需将此添加到脚本

document.getElementsByClassName('tablinks')[0].click()

它模仿了当页面加载

时第一个选项卡上的点击功能

<!DOCTYPE html>
<html>
<style>
body {font-family: "Lato", sans-serif;}
ul.tab {
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    border: 1px solid #ccc;
    background-color: #f1f1f1;
}
/* Float the list items side by side */
ul.tab li {float: left;}
/* Style the links inside the list items */
ul.tab li a {
    display: inline-block;
    color: black;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
    transition: 0.3s;
    font-size: 17px;
}
/* Change background color of links on hover */
ul.tab li a:hover {
    background-color: #ddd;
}
/* Create an active/current tablink class */
ul.tab li a:focus, .active {
    background-color: #ccc;
}
/* Style the tab content */
.tabcontent {
    display: none;
    padding: 6px 12px;
    -webkit-animation: fadeEffect 1s;
    animation: fadeEffect 1s;
}
@-webkit-keyframes fadeEffect {
    from {opacity: 0;}
    to {opacity: 1;}
}
@keyframes fadeEffect {
    from {opacity: 0;}
    to {opacity: 1;}
}
</style>
<body>
<h3>Fade in Tabs</h3>
<ul class="tab">
  <li><a href="#" class="tablinks" onclick="openCity(event, 'London')">London</a></li>
  <li><a href="#" class="tablinks" onclick="openCity(event, 'Paris')">Paris</a></li>
  <li><a href="#" class="tablinks" onclick="openCity(event, 'Tokyo')">Tokyo</a></li>
</ul>
<div id="London" class="tabcontent">
  <h3>London</h3>
  <p>London is the capital city of England.</p>
</div>
<div id="Paris" class="tabcontent">
  <h3>Paris</h3>
  <p>Paris is the capital of France.</p>
</div>
<div id="Tokyo" class="tabcontent">
  <h3>Tokyo</h3>
  <p>Tokyo is the capital of Japan.</p>
</div>
<script>
document.getElementsByClassName('tablinks')[0].click()
function openCity(evt, cityName) {
    var i, tabcontent, tablinks;
    tabcontent = document.getElementsByClassName("tabcontent");
    for (i = 0; i < tabcontent.length; i++) {
        tabcontent[i].style.display = "none";
    }
    tablinks = document.getElementsByClassName("tablinks");
    for (i = 0; i < tablinks.length; i++) {
        tablinks[i].className = tablinks[i].className.replace(" active", "");
    }
    document.getElementById(cityName).style.display = "block";
    evt.currentTarget.className += " active";
}
</script>
</body>
</html>

添加

document.getElementsByClassName('tablinks')[0].click()
at script

添加到CSS:

div[class*="tabcontent"]:first-of-type {
    display: block;
}

将标记更新为:

<a href="#" class="tablinks active" onclick="openCity(event, 'London')">London</a>

或者，也为内容元素实现一个活动类:

/* make this more specific to avoid coloring content elements */
ul.tab li a:focus, ul.tab li a.active {
    background-color: #ccc;
}
/* add this to the CSS */
.tabcontent.active {
    display: block;
}
/* update the markup to add the class */
<div id="London" class="tabcontent active">
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