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

lib/filterClasses.js

Index: lib/filterClasses.js
diff --git a/lib/filterClasses.js b/lib/filterClasses.js
index 417e4d8df3cc13fdd4daa0d6ac14489ad73b92cb..ec7d3d7067494ce7d630844ed57edd194b4641f9 100644
--- a/lib/filterClasses.js
+++ b/lib/filterClasses.js
@@ -359,7 +359,7 @@ ActiveFilter.prototype = extend(Filter, {
   /**
    * 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()
   {
@@ -383,11 +383,11 @@ ActiveFilter.prototype = extend(Filter, {
       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
       {
@@ -413,12 +413,12 @@ ActiveFilter.prototype = extend(Filter, {
           }
 
           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;
@@ -458,7 +458,7 @@ ActiveFilter.prototype = extend(Filter, {
     // 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(/\.+$/, "");
@@ -466,15 +466,16 @@ ActiveFilter.prototype = extend(Filter, {
 
     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("");
   },
 
   /**
@@ -484,16 +485,16 @@ ActiveFilter.prototype = extend(Filter, {
    */
   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;
@@ -513,7 +514,7 @@ ActiveFilter.prototype = extend(Filter, {
   isGeneric()
   {
     return !(this.sitekeys && this.sitekeys.length) &&
-            (!this.domains || this.domains[""]);
+            (!this.domains || this.domains.get(""));
   },
 
   /**