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

lib/elemHide.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 21 matching lines @@
 
 /**
  * Lookup table, keys of the filters by filter text
  * @type {Object}
  */
 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
  * unconditionally matched for all domains.)
  */
 let filterKeyBySelector = Object.create(null);
 
 /**
  * This array caches the keys of filterKeyBySelector table (selectors which
  * unconditionally apply on all domains). It will be null if the cache needs to
@@ skipping 30 matching lines @@
  * @class
  */
 let ElemHide = exports.ElemHide = {
   /**
    * Removes all known filters
    */
   clear()
   {
     filterByKey = [];
     keyByFilter = Object.create(null);
-    filtersByDomain = Object.create(null);
+    filtersByDomain = new Map();
     filterKeyBySelector = Object.create(null);
     unconditionalSelectors = unconditionalFilterKeys = null;
     knownExceptions = Object.create(null);
     exceptions = Object.create(null);
     FilterNotifier.emit("elemhideupdate");
   },
 
   _addToFiltersByDomain(key, filter)
   {
     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;
       else
         filters[key] = false;
     }
   },
 
   /**
    * Add a new element hiding filter
@@ skipping 55 matching lines @@
       delete filterKeyBySelector[filter.selector];
       unconditionalSelectors = unconditionalFilterKeys = null;
       return;
     }
 
     // We haven't found this filter in unconditional filters, look in
     // filtersByDomain.
     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];
     }
   },
 
   /**
    * Removes an element hiding filter
    * @param {ElemHideFilter} filter
    */
   remove(filter)
@@ skipping 158 matching lines @@
     }
 
     let specificOnly = (criteria >= ElemHide.SPECIFIC_ONLY);
     let seenFilters = Object.create(null);
     let currentDomain = domain ? domain.toUpperCase() : "";
     while (true)
     {
       if (specificOnly && currentDomain == "")
         break;
 
-      let filters = filtersByDomain[currentDomain];
+      let filters = filtersByDomain.get(currentDomain);
       if (filters)
       {
         for (let filterKey in filters)
         {
           if (filterKey in seenFilters)
             continue;
           seenFilters[filterKey] = true;
 
           let filter = filters[filterKey];
           if (filter && !this.getException(filter, domain))
@@ skipping 10 matching lines @@
 
       let nextDot = currentDomain.indexOf(".");
       currentDomain = nextDot == -1 ? "" : currentDomain.substr(nextDot + 1);
     }
 
     if (provideFilterKeys)
       return [selectors, filterKeys];
     return selectors;
   }
 };