Issue 5735 - Use JS Map instead of Object for filters which are stored in filtersByDomain in elem...

lib/elemHide.js

Index: lib/elemHide.js
diff --git a/lib/elemHide.js b/lib/elemHide.js
index fc2226343341a5a9859c108faaa51309f2efe483..e99bb8a7f269e4df2370fb95bd950031503540b4 100644
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -39,7 +39,7 @@ let keyByFilter = Object.create(null);
 /**
  * Nested lookup table, filter (or false if inactive) by filter key by domain.
  * (Only contains filters that aren't unconditionally matched for all domains.)
- * @type {Map.<string,Object>}
+ * @type {Map.<string,Map.<string,(Filter|boolean)>>}
  */
 let filtersByDomain = new Map();
 
@@ -107,12 +107,8 @@ let ElemHide = exports.ElemHide = {
     {
       let filters = filtersByDomain.get(domain);
       if (!filters)
-        filtersByDomain.set(domain, filters = Object.create(null));
-
-      if (isIncluded)
-        filters[key] = filter;
-      else
-        filters[key] = false;
+        filtersByDomain.set(domain, filters = new Map());
+      filters.set(key, isIncluded ? filter : false);
     }
   },
 
@@ -185,7 +181,7 @@ let ElemHide = exports.ElemHide = {
     {
       let filters = filtersByDomain.get(domain);
       if (filters)
-        delete filters[key];
+        filters.delete(key);
     }
   },
 
@@ -365,13 +361,12 @@ let ElemHide = exports.ElemHide = {
       let filters = filtersByDomain.get(currentDomain);
       if (filters)
       {
-        for (let filterKey in filters)
+        for (let [filterKey, filter] of filters)
         {
           if (filterKey in seenFilters)
             continue;
           seenFilters[filterKey] = true;
 
-          let filter = filters[filterKey];
           if (filter && !this.getException(filter, domain))
           {
             selectors.push(filter.selector);