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 365 matching lines @@
       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 = new Map();
-        domains.set("", false);
         if (this.ignoreTrailingDot)
           list[0] = list[0].replace(/\.+$/, "");
-        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.

+        domains = new Map([["", false], [list[0], true]]);
       }
       else
       {
         let hasIncludes = false;
         for (let i = 0; i < list.length; i++)
         {
           let domain = list[i];
           if (this.ignoreTrailingDot)
             domain = domain.replace(/\.+$/, "");
           if (domain == "")
@@ skipping 59 matching lines @@
     if (!docDomain)
       return this.domains.get("");
 
     if (this.ignoreTrailingDot)
       docDomain = docDomain.replace(/\.+$/, "");
     docDomain = docDomain.toUpperCase();
 
     while (true)
     {
       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.

+      if (typeof isDomainIncluded != "undefined")
         return isDomainIncluded;
 
       let nextDot = docDomain.indexOf(".");
       if (nextDot < 0)
         break;
       docDomain = docDomain.substr(nextDot + 1);
     }
     return this.domains.get("");
   },
 
@@ skipping 540 matching lines @@
  */
 function ElemHideEmulationFilter(text, domains, selector)
 {
   ElemHideBase.call(this, text, domains, selector);
 }
 exports.ElemHideEmulationFilter = ElemHideEmulationFilter;
 
 ElemHideEmulationFilter.prototype = extend(ElemHideBase, {
   type: "elemhideemulation"
 });