How to get the activated tab?

Question

With bootstrap 5, I was never able to get the activated tab. according to their website I just get the ID of the first button, not the activated tab and nothing else.

var tabEl = document.querySelector('button[data-bs-toggle="tab"]')
tabEl.addEventListener('shown.bs.tab', function (event) {
  alert(event.target.id) // newly activated tab
  // event.relatedTarget // previous active tab
})

<link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js"></script>


<ul class="nav nav-tabs" id="myTab" role="tablist">
  <li class="nav-item" role="presentation">
    <button class="nav-link active" id="home-tab" data-bs-toggle="tab" data-bs-target="#home" type="button" role="tab" aria-controls="home" aria-selected="true">Home</button>
  </li>
  <li class="nav-item" role="presentation">
    <button class="nav-link" id="profile-tab" data-bs-toggle="tab" data-bs-target="#profile" type="button" role="tab" aria-controls="profile" aria-selected="false">Profile</button>
  </li>
  <li class="nav-item" role="presentation">
    <button class="nav-link" id="contact-tab" data-bs-toggle="tab" data-bs-target="#contact" type="button" role="tab" aria-controls="contact" aria-selected="false">Contact</button>
  </li>
</ul>
<div class="tab-content" id="myTabContent">
  <div class="tab-pane fade show active" id="home" role="tabpanel" aria-labelledby="home-tab">...</div>
  <div class="tab-pane fade" id="profile" role="tabpanel" aria-labelledby="profile-tab">...</div>
  <div class="tab-pane fade" id="contact" role="tabpanel" aria-labelledby="contact-tab">...</div>
</div>

I need tabs ID once its related button is clicked.

Answer 1

Your script is only finding the first button[data-bs-toggle="tab"] you need to use document.querySelectorAll('button[data-bs-toggle="tab"]') then loop through the NodeList.

Edit

Selecting the actual active tab-pane element takes a little more legwork. The event.target and event.relatedTarget are the tab buttons and their data-bs-target attribute value is the selector for the associated tab-pane.
Checkout the updated snippet:

var tabEl = document.querySelectorAll('button[data-bs-toggle="tab"]')
//console.log(tabEl)
for (i = 0; i < tabEl.length; i++) {
  tabEl[i].addEventListener('shown.bs.tab', function(event) {
    const activated_pane = document.querySelector(event.target.getAttribute('data-bs-target'))
    const deactivated_pane = document.querySelector(event.relatedTarget.getAttribute('data-bs-target'))

    console.log(activated_pane.id)
    // console.log(deactivated_pane.id)

    // do stuff
    activated_pane.append(' hello ' + activated_pane.id)

  })
}

<link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet">

<ul class="nav nav-tabs" id="myTab" role="tablist">
  <li class="nav-item" role="presentation">
    <button class="nav-link active" id="home-tab" data-bs-toggle="tab" data-bs-target="#home" type="button" role="tab" aria-controls="home" aria-selected="true">Home</button>
  </li>
  <li class="nav-item" role="presentation">
    <button class="nav-link" id="profile-tab" data-bs-toggle="tab" data-bs-target="#profile" type="button" role="tab" aria-controls="profile" aria-selected="false">Profile</button>
  </li>
  <li class="nav-item" role="presentation">
    <button class="nav-link" id="contact-tab" data-bs-toggle="tab" data-bs-target="#contact" type="button" role="tab" aria-controls="contact" aria-selected="false">Contact</button>
  </li>
</ul>
<div class="tab-content" id="myTabContent">
  <div class="tab-pane fade show active" id="home" role="tabpanel" aria-labelledby="home-tab">...</div>
  <div class="tab-pane fade" id="profile" role="tabpanel" aria-labelledby="profile-tab">...</div>
  <div class="tab-pane fade" id="contact" role="tabpanel" aria-labelledby="contact-tab">...</div>
</div>

<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js"></script>

Here's the fiddle.

Answer 2

You are using querySelector, which selects only first element. Use querySelectorAll, which selects all the tabs.

/*
// Using Vanilla JS
var tabEl = document.querySelectorAll('button[data-bs-toggle="tab"]')
tabEl.forEach(function(el){
el.addEventListener('shown.bs.tab', function (event) {
  alert(event.target.id) // newly activated tab
  // event.relatedTarget // previous active tab
})
})

*/

/*
// Using jQuery

*/

$('button[data-bs-toggle="tab"]').on('click', function (e) {     // here is the new selected tab id     
var selectedTabId = e.target.id;   
console.log('tab changed', selectedTabId); 

});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js"></script>


<ul class="nav nav-tabs" id="myTab" role="tablist">
  <li class="nav-item" role="presentation">
    <button class="nav-link active" id="home-tab" data-bs-toggle="tab" data-bs-target="#home" type="button" role="tab" aria-controls="home" aria-selected="true">Home</button>
  </li>
  <li class="nav-item" role="presentation">
    <button class="nav-link" id="profile-tab" data-bs-toggle="tab" data-bs-target="#profile" type="button" role="tab" aria-controls="profile" aria-selected="false">Profile</button>
  </li>
  <li class="nav-item" role="presentation">
    <button class="nav-link" id="contact-tab" data-bs-toggle="tab" data-bs-target="#contact" type="button" role="tab" aria-controls="contact" aria-selected="false">Contact</button>
  </li>
</ul>
<div class="tab-content" id="myTabContent">
  <div class="tab-pane fade show active" id="home" role="tabpanel" aria-labelledby="home-tab">...</div>
  <div class="tab-pane fade" id="profile" role="tabpanel" aria-labelledby="profile-tab">...</div>
  <div class="tab-pane fade" id="contact" role="tabpanel" aria-labelledby="contact-tab">...</div>
</div>