minor symfony#9892 Use <button> instead of <a> for JavaScript interactive buttons (Calinou)

This PR was merged into the 2.8 branch.

Discussion
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Use <button> instead of <a> for JavaScript interactive buttons

This removes the need to call `preventDefault()` to disable the default action of `<a>` elements, since `<button type="button">` has no default action whatsoever.

See also [this Stack Overflow question](https://stackoverflow.com/questions/469059/button-vs-input-type-button-which-to-use) about the `<button>` HTML tag.

Commits
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87db1b6 Use <button> instead of <a> for JavaScript interactive buttons

Author: javiereguiluz

form/form_collections.rst

@@ -353,8 +353,8 @@ will be show next):
     var $collectionHolder;
 
     // setup an "add a tag" link
-    var $addTagLink = $('<a href="#" class="add_tag_link">Add a tag</a>');
-    var $newLinkLi = $('<li></li>').append($addTagLink);
+    var $addTagButton = $('<button type="button" class="add_tag_link">Add a tag</a>');
+    var $newLinkLi = $('<li></li>').append($addTagButton);
 
     jQuery(document).ready(function() {
         // Get the ul that holds the collection of tags
@@ -367,10 +367,7 @@ will be show next):
         // index when inserting a new item (e.g. 2)
         $collectionHolder.data('index', $collectionHolder.find(':input').length);
 
-        $addTagLink.on('click', function(e) {
-            // prevent the link from creating a "#" on the URL
-            e.preventDefault();
-
+        $addTagButton.on('click', function(e) {
             // add a new tag form (see next code block)
             addTagForm($collectionHolder, $newLinkLi);
         });
@@ -619,7 +616,7 @@ Template Modifications
 
 The ``allow_delete`` option means that if an item of a collection
 isn't sent on submission, the related data is removed from the collection
-on the server. In order for this to work in an HTML form, you must remove 
+on the server. In order for this to work in an HTML form, you must remove
 the DOM element for the collection item to be removed, before submitting
 the form.
 
@@ -651,13 +648,10 @@ The ``addTagFormDeleteLink()`` function will look something like this:
 .. code-block:: javascript
 
     function addTagFormDeleteLink($tagFormLi) {
-        var $removeFormA = $('<a href="#">delete this tag</a>');
-        $tagFormLi.append($removeFormA);
-
-        $removeFormA.on('click', function(e) {
-            // prevent the link from creating a "#" on the URL
-            e.preventDefault();
+        var $removeFormButton = $('<button type="button">Delete this tag</a>');
+        $tagFormLi.append($removeFormButton);
 
+        $removeFormButton.on('click', function(e) {
             // remove the li for the tag form
             $tagFormLi.remove();
         });

reference/forms/types/collection.rst

@@ -168,7 +168,6 @@ you need is this JavaScript code:
     // add-collection-widget.js
     jQuery(document).ready(function () {
         jQuery('.add-another-collection-widget').click(function (e) {
-            e.preventDefault();
             var list = jQuery(jQuery(this).attr('data-list'));
             // Try to find the counter of the list
             var counter = list.data('widget-counter') | list.children().length;
@@ -211,7 +210,7 @@ And update the template as follows:
         {% endfor %}
         </ul>
 
-        <a href="#"
+        <button type="button"
             class="add-another-collection-widget"
             data-list="#email-fields-list">Add another email</a>