Use try...catch block with underscore.js template.

readthedocs/core/static-src/core/js/doc-embed/search.js

@@ -7,6 +7,33 @@ var xss = require('xss/lib/index');
 var MAX_RESULT_PER_SECTION = 3;
 var MAX_SUBSTRING_LIMIT = 100;
 
+/**
+ * Use try...catch block to append html to contents
+ *
+ * @param {Object} contents html element on which additional html is be appended
+ * @param {String} template underscore.js template string
+ * @param {Object} data template vars and their values
+ */
+function append_html_to_contents(contents, template, data) {
+    // underscore.js throws variable not defined error
+    // because of change of syntax in new versions.
+    // See: https://stackoverflow.com/a/25881231/8601393
+    try {
+        // this is the pre-1.7 syntax from Underscore.js
+        contents.append(
+            $u.template(
+                template,
+                data
+            )
+        );
+    }
+    catch (error) {
+        // this is the new syntax
+        contents.append(
+            $u.template(template)(data)
+        );
+    }
+}
 
 /*
  * Search query override for hitting our local API instead of the standard
@@ -129,15 +156,14 @@ function attach_elastic_search_query(data) {
                                     }
                                 }
 
-                                contents.append(
-                                    $u.template(
-                                        section_template,
-                                        {
-                                            section_subtitle_link: section_subtitle_link,
-                                            section_subtitle: section_subtitle,
-                                            section_content: section_content
-                                        }
-                                    )
+                                append_html_to_contents(
+                                    contents,
+                                    section_template,
+                                    {
+                                        section_subtitle_link: section_subtitle_link,
+                                        section_subtitle: section_subtitle,
+                                        section_content: section_content
+                                    }
                                 );
                             }
 
@@ -167,15 +193,14 @@ function attach_elastic_search_query(data) {
                                 // domain_content = type_display -- name -- in doc_display
                                 domain_content = domain._source.type_display + " -- " + domain_name + " -- in " + domain._source.doc_display;
 
-                                contents.append(
-                                    $u.template(
-                                        domain_template,
-                                        {
-                                            domain_subtitle_link: domain_subtitle_link,
-                                            domain_subtitle: domain_subtitle,
-                                            domain_content: domain_content
-                                        }
-                                    )
+                                append_html_to_contents(
+                                    contents,
+                                    domain_template,
+                                    {
+                                        domain_subtitle_link: domain_subtitle_link,
+                                        domain_subtitle: domain_subtitle,
+                                        domain_content: domain_content
+                                    }
                                 );
                             }