Add event.relatedTarget + `data-*` example to Modal docs

Fixes #14245

docs/_includes/js/modal.html

@@ -211,6 +211,86 @@
 <div class="modal" tabindex="-1" role="dialog" aria-labelledby="" aria-hidden="true">
   ...
 </div>
+{% endhighlight %}
+
+  <h2 id="modals-related-target">Varying modal content based on trigger button</h2>
+  <p>Have a bunch of buttons that all trigger the same modal, just with slightly different contents? Use <code>event.relatedTarget</code> and <a href="https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Using_data_attributes">HTML <code>data-*</code> attributes</a> (possibly <a href="http://api.jquery.com/data/">via jQuery</a>) to vary the contents of the modal depending on which button was clicked. See the Modal Events docs for details on <code>relatedTarget</code>,</p>
+  <div class="bs-example" style="padding-bottom: 24px;">
+    <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal" data-whatever="@mdo">Open modal for @mdo</button>
+    <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal" data-whatever="@fat">Open modal for @fat</button>
+    <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal" data-whatever="@twbootstrap">Open modal for @twbootstrap</button>
+    ...more buttons...
+
+    <div class="modal fade" id="exampleModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">
+      <div class="modal-dialog">
+        <div class="modal-content">
+          <div class="modal-header">
+            <button type="button" class="close" data-dismiss="modal"><span aria-hidden="true">&times;</span><span class="sr-only">Close</span></button>
+            <h4 class="modal-title" id="exampleModalLabel">New message</h4>
+          </div>
+          <div class="modal-body">
+            <form role="form">
+              <div class="form-group">
+                <label for="recipient-name" class="control-label">Recipient:</label>
+                <input type="text" class="form-control" id="recipient-name">
+              </div>
+              <div class="form-group">
+                <label for="message-text" class="control-label">Message:</label>
+                <textarea class="form-control" id="message-text"></textarea>
+              </div>
+            </form>
+          </div>
+          <div class="modal-footer">
+            <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
+            <button type="button" class="btn btn-primary">Send message</button>
+          </div>
+        </div>
+      </div>
+    </div><!-- /.modal -->
+  </div><!-- /.bs-example -->
+{% highlight html %}
+<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal" data-whatever="@mdo">Open modal for @mdo</button>
+<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal" data-whatever="@fat">Open modal for @fat</button>
+<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal" data-whatever="@twbootstrap">Open modal for @twbootstrap</button>
+...more buttons...
+
+<div class="modal fade" id="exampleModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">
+  <div class="modal-dialog">
+    <div class="modal-content">
+      <div class="modal-header">
+        <button type="button" class="close" data-dismiss="modal"><span aria-hidden="true">&times;</span><span class="sr-only">Close</span></button>
+        <h4 class="modal-title" id="exampleModalLabel">New message</h4>
+      </div>
+      <div class="modal-body">
+        <form role="form">
+          <div class="form-group">
+            <label for="recipient-name" class="control-label">Recipient:</label>
+            <input type="text" class="form-control" id="recipient-name">
+          </div>
+          <div class="form-group">
+            <label for="message-text" class="control-label">Message:</label>
+            <textarea class="form-control" id="message-text"></textarea>
+          </div>
+        </form>
+      </div>
+      <div class="modal-footer">
+        <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
+        <button type="button" class="btn btn-primary">Send message</button>
+      </div>
+    </div>
+  </div>
+</div>
+{% endhighlight %}
+{% highlight js %}
+$('#exampleModal').on('show.bs.modal', function (event) {
+  var button = $(event.relatedTarget) // Button that triggered the modal
+  var recipient = button.data('whatever') // Extract info from data-* attributes
+  // If necessary, you could initiate an AJAX request here (and then do the updating in a callback).
+  // Update the modal's content. We'll use jQuery here, but you could use a data binding library or other methods instead.
+  var modal = $(this)
+  modal.find('.modal-title').text('New message to ' + recipient)
+  modal.find('.modal-body input').val(recipient)
+})
 {% endhighlight %}
 
   <h2 id="modals-usage">Usage</h2>

docs/_includes/nav/javascript.html

@@ -17,6 +17,7 @@
     <li><a href="#modals-examples">Examples</a></li>
     <li><a href="#modals-sizes">Sizes</a></li>
     <li><a href="#modals-remove-animation">Remove animation</a></li>
+    <li><a href="#modals-related-target">Varying content based on trigger button</a></li>
     <li><a href="#modals-usage">Usage</a></li>
   </ul>
 </li>

docs/assets/js/src/application.js

@@ -109,6 +109,17 @@
       }, 3000)
     })
 
+    // Modal relatedTarget demo
+    $('#exampleModal').on('show.bs.modal', function (event) {
+      var button = $(event.relatedTarget) // Button that triggered the modal
+      var recipient = button.data('whatever') // Extract info from data-* attributes
+      // If necessary, you could initiate an AJAX request here (and then do the updating in a callback).
+      // Update the modal's content. We'll use jQuery here, but you could use a data binding library or other methods instead.
+      var modal = $(this)
+      modal.find('.modal-title').text('New message to ' + recipient)
+      modal.find('.modal-body input').val(recipient)
+    })
+
     // Activate animated progress bar
     $('.bs-docs-activate-animated-progressbar').on('click', function () {
       $(this).siblings('.progress').find('.progress-bar-striped').toggleClass('active')