Issue 5735 - Use JS Map instead of Object for global filtersByDomain in elemHide.js

lib/elemHide.js

Index: lib/elemHide.js
diff --git a/lib/elemHide.js b/lib/elemHide.js
index a6d2c5a7a27c05e91a0186320b560f3db405e721..fc2226343341a5a9859c108faaa51309f2efe483 100644
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -39,9 +39,9 @@ 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 {Object}
+ * @type {Map.<string,Object>}
  */
-let filtersByDomain = Object.create(null);
+let filtersByDomain = new Map();
 
 /**
  * Lookup table, filter key by selector. (Only used for selectors that are
@@ -92,7 +92,7 @@ let ElemHide = exports.ElemHide = {
   {
     filterByKey = [];
     keyByFilter = Object.create(null);
-    filtersByDomain = Object.create(null);
+    filtersByDomain = new Map();
     filterKeyBySelector = Object.create(null);
     unconditionalSelectors = unconditionalFilterKeys = null;
     knownExceptions = Object.create(null);
@@ -105,9 +105,9 @@ let ElemHide = exports.ElemHide = {
     let domains = filter.domains || defaultDomains;
     for (let [domain, isIncluded] of domains)
     {
-      let filters = filtersByDomain[domain];
+      let filters = filtersByDomain.get(domain);
       if (!filters)
-        filters = filtersByDomain[domain] = Object.create(null);
+        filtersByDomain.set(domain, filters = Object.create(null));

[sergei, 2017/09/21 12:00:26]

filters are changed in https://codereview.adblockplus.org/29551635/

 
       if (isIncluded)
         filters[key] = filter;
@@ -183,7 +183,7 @@ let ElemHide = exports.ElemHide = {
     let domains = filter.domains || defaultDomains;
     for (let domain of domains.keys())
     {
-      let filters = filtersByDomain[domain];
+      let filters = filtersByDomain.get(domain);
       if (filters)
         delete filters[key];
     }
@@ -362,7 +362,7 @@ let ElemHide = exports.ElemHide = {
       if (specificOnly && currentDomain == "")
         break;
 
-      let filters = filtersByDomain[currentDomain];
+      let filters = filtersByDomain.get(currentDomain);
       if (filters)
       {
         for (let filterKey in filters)