Javascript HTML 中的 TABS：默认选择第一个 TAB
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TABS in HTML: Select first TAB by default
提问by KP Joy
I am trying TABBING in HTML. I am using a tutorial from W3SCHOOLS.
我正在尝试在 HTML 中 TABBING。我正在使用W3SCHOOLS的教程。
Following is the source code. It works fine but the problem I am facing is to select the first tab by default which is missing in this tutorial. I want that first tab should be automatically selected when the page loads and the content of that should be displayed automatically.
以下是源代码。它工作正常，但我面临的问题是默认选择本教程中缺少的第一个选项卡。我希望在页面加载时应该自动选择第一个选项卡，并且应该自动显示其内容。
<!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>
What change should I make in Javascript to select the first tab by default? I tried the following line inside for loop but did not work:
默认情况下，我应该在 Javascript 中进行哪些更改以选择第一个选项卡？我在 for 循环中尝试了以下行，但没有用：
tablinks[0].className += " active";
回答by Sanjeev Kumar
回答by TheBreakthrough
A purely javascript way of doing it, just add this to your script
一种纯粹的 javascript 方式，只需将其添加到您的脚本中
document.getElementsByClassName('tablinks')[0].click()
It imitates a click function on your first tab when the page loads
当页面加载时，它会在您的第一个选项卡上模仿点击功能
回答by Mark
<!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>added
添加
document.getElementsByClassName('tablinks')[0].click() 在脚本回答by isherwood
Add this to the CSS:
将此添加到 CSS：
div[class*="tabcontent"]:first-of-type {
display: block;
}
Update the markup to this:
将标记更新为：
<a href="#" class="tablinks active" onclick="openCity(event, 'London')">London</a>
Alternatively, implement an active class for the content elements, too:
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">
