introduce a utils helper for prototype inheritance

2 files changed, 11 insertions, 3 deletions

diff --git a/lib/completion.js b/lib/completion.js
index 6aec9e83..3c43f28b 100644
--- a/lib/completion.js
+++ b/lib/completion.js
@@ -410,7 +410,7 @@ var completion = (function() {
     AsyncFuzzyUrlCompleter.call(this);
     this.maxResults = maxResults || 1000;
   }
-  FuzzyHistoryCompleter.prototype = new AsyncFuzzyUrlCompleter;
+  utils.extend(AsyncFuzzyUrlCompleter, FuzzyHistoryCompleter);
   FuzzyHistoryCompleter.prototype.refresh = function() {
     this.resetCache();
     this.fetchFromPort('getHistory', { maxResults: this.maxResults }, function(msg) {
@@ -424,7 +424,7 @@ var completion = (function() {
   var FuzzyBookmarkCompleter = function() {
     AsyncFuzzyUrlCompleter.call(this);
   }
-  FuzzyBookmarkCompleter.prototype = new AsyncFuzzyUrlCompleter;
+  utils.extend(AsyncFuzzyUrlCompleter, FuzzyBookmarkCompleter);
   FuzzyBookmarkCompleter.prototype.refresh = function() {
     this.resetCache();
     this.fetchFromPort('getAllBookmarks', {}, function(msg) {
@@ -439,7 +439,7 @@ var completion = (function() {
   var FuzzyTabCompleter = function() {
     AsyncFuzzyUrlCompleter.call(this);
   }
-  FuzzyTabCompleter.prototype = new AsyncFuzzyUrlCompleter;
+  utils.extend(AsyncFuzzyUrlCompleter, FuzzyTabCompleter);
   FuzzyTabCompleter.prototype.createAction = function(match) {
     var open = function() {
       chrome.extension.sendRequest({ handler: 'selectSpecificTab', id: match.tab.id });
diff --git a/lib/utils.js b/lib/utils.js
index 9b5cfcb9..7ed7c9ad 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -39,6 +39,14 @@ var utils = {
     return document.evaluate(xpath, document.documentElement, namespaceResolver, resultType, null);
   },
 
+  /** Sets up prototype inheritance */
+  extend: function(base, sub) {
+    function surrogateCtor() { }
+    surrogateCtor.prototype = base.prototype;
+    sub.prototype = new surrogateCtor();
+    sub.prototype.constructor = sub;
+  },
+
   /** Creates a single DOM element from :html */
   createElementFromHtml: function(html) {
     var tmp = document.createElement("div");