Bootstrap 4 Tutorial

Bootstrap 4 JS Alert

Last modified on: October 27, 2024

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<h2 class="relative p-1 rounded-sm flex items-center justify-center bg-token-main-surface-primary text-token-text-primary h-8 w-8">JavaScript Alerts in Bootstrap 4</h2>
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<p>Bootstrap 4 itself doesn&rsquo;t provide JavaScript alerts, but it has a styled <strong>alert component</strong> that can be enhanced with JavaScript to create dismissible alert messages. Here&rsquo;s how to create and control alerts using Bootstrap&rsquo;s alert classes combined with JavaScript.</p>
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<h3>1. Creating a Bootstrap Alert</h3>
<p>To start, define an alert element in HTML using Bootstrap classes. This alert will appear when the page loads:</p>
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<pre class="language-markup"><code>&lt;div class="alert alert-warning alert-dismissible fade show" role="alert"&gt;
  &lt;strong&gt;Warning!&lt;/strong&gt; This is a Bootstrap 4 alert message.
  &lt;button type="button" class="close" data-dismiss="alert" aria-label="Close"&gt;
    &lt;span aria-hidden="true"&gt;&amp;times;&lt;/span&gt;
  &lt;/button&gt;
&lt;/div&gt;
</code></pre>
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<ul>
<li><strong>Classes Explained</strong>:
<ul>
<li><code>.alert</code>: Base class for all alert messages.</li>
<li><code>.alert-warning</code>: Color style for a warning alert (use <code>.alert-success</code>, <code>.alert-danger</code>, etc., for other types).</li>
<li><code>.alert-dismissible</code>: Allows the alert to be dismissed.</li>
<li><code>.fade</code> and <code>.show</code>: Used together to animate the alert.</li>
<li><code>.close</code>: Styles the close button.</li>
<li><code>data-dismiss="alert"</code>: Tells Bootstrap that this button will close the alert when clicked.</li>
</ul>
</li>
</ul>
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<h3>2. Triggering Alerts with JavaScript</h3>
<p>You can also use JavaScript to dynamically create and display alerts on an event (e.g., a button click).</p>
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<pre class="language-markup"><code>&lt;button onclick="showAlert()" class="btn btn-primary"&gt;Show Alert&lt;/button&gt;

&lt;script&gt;
  function showAlert() {
    // Create the alert div
    const alertDiv = document.createElement('div');
    alertDiv.className = 'alert alert-success alert-dismissible fade show';
    alertDiv.role = 'alert';
    alertDiv.innerHTML = `
      &lt;strong&gt;Success!&lt;/strong&gt; You have triggered this alert.
      &lt;button type="button" class="close" data-dismiss="alert" aria-label="Close"&gt;
        &lt;span aria-hidden="true"&gt;&amp;times;&lt;/span&gt;
      &lt;/button&gt;
    `;

// Append the alert to a container (e.g., at the top of the body)
    document.body.prepend(alertDiv);

// Automatically remove the alert after 3 seconds
    setTimeout(() =&gt; {
      alertDiv.classList.remove('show');
      alertDiv.classList.add('fade');
      setTimeout(() =&gt; alertDiv.remove(), 150); // Allow fade-out before removal
    }, 3000);
  }
&lt;/script&gt;
</code></pre>
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<h3>Explanation of the Code</h3>
<ol>
<li><strong>JavaScript Function</strong>: <code>showAlert()</code> creates a new alert div with Bootstrap classes and adds it to the top of the page.</li>
<li><strong>Auto Removal</strong>: <code>setTimeout</code> automatically removes the alert after a specified duration (3 seconds here).</li>
</ol>
<h3>&nbsp;</h3>
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