Issue 5735 - Use JS Map instead of Object for property domains of Filter objects

lib/filterClasses.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 341 matching lines @@
   /**
    * Determines whether domainSource is already upper-case,
    * can be overridden by subclasses.
    * @type {boolean}
    */
   domainSourceIsUpperCase: false,
 
   /**
    * Map containing domains that this filter should match on/not match
    * on or null if the filter should match on all domains
-   * @type {Object}
+   * @type {?Map.<string,boolean>}
    */
   get domains()
   {
     // Despite this property being cached, the getter is called
     // several times on Safari, due to WebKit bug 132872
     let prop = Object.getOwnPropertyDescriptor(this, "domains");
     if (prop)
       return prop.value;
 
     let domains = null;
 
     if (this.domainSource)
     {
       let source = this.domainSource;
       if (!this.domainSourceIsUpperCase)
       {
         // RegExpFilter already have uppercase domains
         source = source.toUpperCase();
       }
       let list = source.split(this.domainSeparator);
       if (list.length == 1 && list[0][0] != "~")
       {
         // Fast track for the common one-domain scenario
-        domains = Object.create(null);
-        domains[""] = false;
+        domains = new Map();
+        domains.set("", false);
         if (this.ignoreTrailingDot)
           list[0] = list[0].replace(/\.+$/, "");
-        domains[list[0]] = true;
+        domains.set(list[0], true);

[Wladimir Palant, 2017/09/21 08:11:44]

You can initialize the Map object immediately: new Map([["", false], [list[0],
true]])

[sergei, 2017/09/21 10:50:34]

Done. BTW, I would like to pay attention to the impact of these tree additional
arrays on the performance and memory usage.

[Wladimir Palant, 2017/09/21 10:53:01]

Feel free to measure that. I assume that the JS engine uses shortcuts here so
that the arrays aren't actually created.

       }
       else
       {
         let hasIncludes = false;
         for (let i = 0; i < list.length; i++)
         {
           let domain = list[i];
           if (this.ignoreTrailingDot)
             domain = domain.replace(/\.+$/, "");
           if (domain == "")
             continue;
 
           let include;
           if (domain[0] == "~")
           {
             include = false;
             domain = domain.substr(1);
           }
           else
           {
             include = true;
             hasIncludes = true;
           }
 
           if (!domains)
-            domains = Object.create(null);
+            domains = new Map();
 
-          domains[domain] = include;
+          domains.set(domain, include);
         }
         if (domains)
-          domains[""] = !hasIncludes;
+          domains.set("", !hasIncludes);
       }
 
       this.domainSource = null;
     }
 
     Object.defineProperty(this, "domains", {value: domains, enumerable: true});
     return this.domains;
   },
 
   /**
@@ skipping 19 matching lines @@
       return false;
     }
 
     // If no domains are set the rule matches everywhere
     if (!this.domains)
       return true;
 
     // If the document has no host name, match only if the filter
     // isn't restricted to specific domains
     if (!docDomain)
-      return this.domains[""];
+      return this.domains.get("");
 
     if (this.ignoreTrailingDot)
       docDomain = docDomain.replace(/\.+$/, "");
     docDomain = docDomain.toUpperCase();
 
     while (true)
     {
-      if (docDomain in this.domains)
-        return this.domains[docDomain];
+      let isDomainIncluded = this.domains.get(docDomain);
+      if (isDomainIncluded != undefined)

[Wladimir Palant, 2017/09/21 08:11:44]

We usually use the typeof operator: `typeof isDomainIncluded != "undefined"`

[sergei, 2017/09/21 10:50:34]

Acknowledged.

+        return isDomainIncluded;
 
       let nextDot = docDomain.indexOf(".");
       if (nextDot < 0)
         break;
       docDomain = docDomain.substr(nextDot + 1);
     }
-    return this.domains[""];
+    return this.domains.get("");
   },
 
   /**
    * Checks whether this filter is active only on a domain and its subdomains.
    * @param {string} docDomain
    * @return {boolean}
    */
   isActiveOnlyOnDomain(docDomain)
   {
-    if (!docDomain || !this.domains || this.domains[""])
+    if (!docDomain || !this.domains || this.domains.get(""))
       return false;
 
     if (this.ignoreTrailingDot)
       docDomain = docDomain.replace(/\.+$/, "");
     docDomain = docDomain.toUpperCase();
 
-    for (let domain in this.domains)
+    for (let [domain, isIncluded] of this.domains)
     {
-      if (this.domains[domain] && domain != docDomain)
+      if (isIncluded && domain != docDomain)
       {
         if (domain.length <= docDomain.length)
           return false;
 
         if (!domain.endsWith("." + docDomain))
           return false;
       }
     }
 
     return true;
   },
 
   /**
    * Checks whether this filter is generic or specific
    * @return {boolean}
    */
   isGeneric()
   {
     return !(this.sitekeys && this.sitekeys.length) &&
-            (!this.domains || this.domains[""]);
+            (!this.domains || this.domains.get(""));
   },
 
   /**
    * See Filter.serialize()
    * @inheritdoc
    */
   serialize(buffer)
   {
     if (this._disabled || this._hitCount || this._lastHit)
     {
@@ skipping 493 matching lines @@
  */
 function ElemHideEmulationFilter(text, domains, selector)
 {
   ElemHideBase.call(this, text, domains, selector);
 }
 exports.ElemHideEmulationFilter = ElemHideEmulationFilter;
 
 ElemHideEmulationFilter.prototype = extend(ElemHideBase, {
   type: "elemhideemulation"
 });