Issue 5735 - Use JS Map instead of Object for Filter.knownFilters

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 61 matching lines @@
   },
 
   toString()
   {
     return this.text;
   }
 };
 
 /**
  * Cache for known filters, maps string representation to filter objects.
- * @type {Object}
+ * @type {Map.<string,Filter>}
  */
-Filter.knownFilters = Object.create(null);
+Filter.knownFilters = new Map();
 
 /**
  * Regular expression that element hiding filters should match
  * @type {RegExp}
  */
 Filter.elemhideRegExp = /^([^/*|@"!]*?)#([@?])?#(.+)$/;
 /**
  * Regular expression that RegExp filters specified as RegExps should match
  * @type {RegExp}
  */
 Filter.regexpRegExp = /^(@@)?\/.*\/(?:\$~?[\w-]+(?:=[^,\s]+)?(?:,~?[\w-]+(?:=[^,\s]+)?)*)?$/;
 /**
  * Regular expression that options on a RegExp filter should match
  * @type {RegExp}
  */
 Filter.optionsRegExp = /\$(~?[\w-]+(?:=[^,\s]+)?(?:,~?[\w-]+(?:=[^,\s]+)?)*)$/;
 
 /**
  * Creates a filter of correct type from its text representation - does the
  * basic parsing and calls the right constructor then.
  *
  * @param {string} text   as in Filter()
  * @return {Filter}
  */
 Filter.fromText = function(text)
 {
-  if (text in Filter.knownFilters)
-    return Filter.knownFilters[text];
+  let ret = Filter.knownFilters.get(text);
+  if (ret)

[kzar, 2017/09/20 12:30:24]

Just an observation since I don't think it matters, but this behaviour is
slightly different. If we cached a falsey value for a filter previously we would
have returned it but now we won't.

+    return ret;
 
-  let ret;
   let match = (text.includes("#") ? Filter.elemhideRegExp.exec(text) : null);
   if (match)
   {
     let propsMatch;
     if (!match[2] &&
         (propsMatch = /\[-abp-properties=(["'])([^"']+)\1\]/.exec(match[3])))
     {
       // This is legacy CSS properties syntax, convert to current syntax
       let prefix = match[3].substr(0, propsMatch.index);
       let expression = propsMatch[2];
       let suffix = match[3].substr(propsMatch.index + propsMatch[0].length);
       return Filter.fromText(`${match[1]}#?#` +
           `${prefix}:-abp-properties(${expression})${suffix}`);
     }
 
     ret = ElemHideBase.fromText(
       text, match[1], match[2], match[3]
     );
   }
   else if (text[0] == "!")
     ret = new CommentFilter(text);
   else
     ret = RegExpFilter.fromText(text);
 
-  Filter.knownFilters[ret.text] = ret;
+  Filter.knownFilters.set(ret.text, ret);
   return ret;
 };
 
 /**
  * Deserializes a filter
  *
  * @param {Object}  obj map of serialized properties and their values
  * @return {Filter} filter or null if the filter couldn't be created
  */
 Filter.fromObject = function(obj)
@@ skipping 870 matching lines @@
  */
 function ElemHideEmulationFilter(text, domains, selector)
 {
   ElemHideBase.call(this, text, domains, selector);
 }
 exports.ElemHideEmulationFilter = ElemHideEmulationFilter;
 
 ElemHideEmulationFilter.prototype = extend(ElemHideBase, {
   type: "elemhideemulation"
 });