Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/comment/js/comment-new-indicator.js

@@ -0,0 +1,87 @@
+/**
+ * @file
+ * Attaches behaviors for the Comment module's "new" indicator.
+ *
+ * May only be loaded for authenticated users, with the History module
+ * installed.
+ */
+
+(function ($, Drupal, window) {
+
+  "use strict";
+
+  /**
+   * Render "new" comment indicators wherever necessary.
+   *
+   * @type {Drupal~behavior}
+   */
+  Drupal.behaviors.commentNewIndicator = {
+    attach: function (context) {
+      // Collect all "new" comment indicator placeholders (and their corresponding
+      // node IDs) newer than 30 days ago that have not already been read after
+      // their last comment timestamp.
+      var nodeIDs = [];
+      var $placeholders = $(context)
+        .find('[data-comment-timestamp]')
+        .once('history')
+        .filter(function () {
+          var $placeholder = $(this);
+          var commentTimestamp = parseInt($placeholder.attr('data-comment-timestamp'), 10);
+          var nodeID = $placeholder.closest('[data-history-node-id]').attr('data-history-node-id');
+          if (Drupal.history.needsServerCheck(nodeID, commentTimestamp)) {
+            nodeIDs.push(nodeID);
+            return true;
+          }
+          else {
+            return false;
+          }
+        });
+
+      if ($placeholders.length === 0) {
+        return;
+      }
+
+      // Fetch the node read timestamps from the server.
+      Drupal.history.fetchTimestamps(nodeIDs, function () {
+        processCommentNewIndicators($placeholders);
+      });
+    }
+  };
+
+  function processCommentNewIndicators($placeholders) {
+    var isFirstNewComment = true;
+    var newCommentString = Drupal.t('new');
+    var $placeholder;
+
+    $placeholders.each(function (index, placeholder) {
+      $placeholder = $(placeholder);
+      var timestamp = parseInt($placeholder.attr('data-comment-timestamp'), 10);
+      var $node = $placeholder.closest('[data-history-node-id]');
+      var nodeID = $node.attr('data-history-node-id');
+      var lastViewTimestamp = Drupal.history.getLastRead(nodeID);
+
+      if (timestamp > lastViewTimestamp) {
+        // Turn the placeholder into an actual "new" indicator.
+        var $comment = $(placeholder)
+          .removeClass('hidden')
+          .text(newCommentString)
+          .closest('.comment')
+          // Add 'new' class to the comment, so it can be styled.
+          .addClass('new');
+
+        // Insert "new" anchor just before the "comment-<cid>" anchor if
+        // this is the first new comment in the DOM.
+        if (isFirstNewComment) {
+          isFirstNewComment = false;
+          $comment.prev().before('<a id="new" />');
+          // If the URL points to the first new comment, then scroll to that
+          // comment.
+          if (window.location.hash === '#new') {
+            window.scrollTo(0, $comment.offset().top - Drupal.displace.offsets.top);
+          }
+        }
+      }
+    });
+  }
+
+})(jQuery, Drupal, window);