Issue 6741 - Use ES2015 classes in lib/filterClasses.js

lib/filterClasses.js

Index: lib/filterClasses.js
===================================================================
--- a/lib/filterClasses.js
+++ b/lib/filterClasses.js
@@ -17,70 +17,67 @@
 
 "use strict";
 
 /**
  * @fileOverview Definition of Filter class and its subclasses.
  */
 
 const {FilterNotifier} = require("./filterNotifier");
-const {extend} = require("./coreUtils");
 const {filterToRegExp} = require("./common");
 
 /**
  * Abstract base class for filters
- *
- * @param {string} text   string representation of the filter
- * @constructor
  */
-function Filter(text)
-{
-  this.text = text;
-  this.subscriptions = [];
-}
-exports.Filter = Filter;
-
-Filter.prototype =
+class Filter
 {
   /**
-   * String representation of the filter
-   * @type {string}
+   * @param {string} text   string representation of the filter
    */
-  text: null,
+  constructor(text)
+  {
+    /**

[Manish Jethani, 2018/06/09 13:03:32]

For instance properties that are always assigned in the constructor, we can keep
the documentation in the constructor as well. The prototype does not have these
properties now.

+     * String representation of the filter
+     * @type {string}
+     */
+    this.text = text;
 
-  /**
-   * Filter subscriptions the filter belongs to
-   * @type {Subscription[]}
-   */
-  subscriptions: null,
+    /**
+     * Filter subscriptions the filter belongs to
+     * @type {Subscription[]}
+     */
+    this.subscriptions = [];
+  }
 
   /**
    * Filter type as a string, e.g. "blocking".
    * @type {string}
    */
   get type()
   {
     throw new Error("Please define filter type in the subclass");
-  },
+  }
 
   /**
    * Serializes the filter to an array of strings for writing out on the disk.
    * @param {string[]} buffer  buffer to push the serialization results into
    */
   serialize(buffer)
   {
     buffer.push("[Filter]");
     buffer.push("text=" + this.text);
-  },
+  }
 
   toString()
   {
     return this.text;
   }
-};
+}
+
+exports.Filter = Filter;
 
 /**
  * Cache for known filters, maps string representation to filter objects.
  * @type {Map.<string,Filter>}
  */
 Filter.knownFilters = new Map();
 
 /**
@@ -235,168 +232,152 @@
 
 /**
  * @see filterToRegExp
  */
 Filter.toRegExp = filterToRegExp;
 
 /**
  * Class for invalid filters
- * @param {string} text see Filter()
- * @param {string} reason Reason why this filter is invalid
- * @constructor
- * @augments Filter
  */
-function InvalidFilter(text, reason)
+class InvalidFilter extends Filter
 {
-  Filter.call(this, text);
+  /**
+   * @param {string} text see Filter()
+   * @param {string} reason Reason why this filter is invalid
+   */
+  constructor(text, reason)
+  {
+    super(text);
 
-  this.reason = reason;
-}
-exports.InvalidFilter = InvalidFilter;
+    /**
+     * Reason why this filter is invalid
+     * @type {string}
+     */
+    this.reason = reason;
+  }
 
-InvalidFilter.prototype = extend(Filter, {
-  type: "invalid",
-
-  /**
-   * Reason why this filter is invalid
-   * @type {string}
-   */
-  reason: null,
+  get type()

[Manish Jethani, 2018/06/09 13:03:32]

This needs to be a getter now.

+  {
+    return "invalid";
+  }
 
   /**
    * See Filter.serialize()
    * @inheritdoc
    */
   serialize(buffer) {}
-});
+}
+
+exports.InvalidFilter = InvalidFilter;
 
 /**
  * Class for comments
- * @param {string} text see Filter()
- * @constructor
- * @augments Filter
  */
-function CommentFilter(text)
+class CommentFilter extends Filter
 {
-  Filter.call(this, text);
-}
-exports.CommentFilter = CommentFilter;
+  /**
+   * @param {string} text see Filter()
+   */
+  constructor(text)
+  {
+    super(text);
+  }
 
-CommentFilter.prototype = extend(Filter, {
-  type: "comment",
+  get type()
+  {
+    return "comment";
+  }
 
   /**
    * See Filter.serialize()
    * @inheritdoc
    */
   serialize(buffer) {}
-});
+}
+
+exports.CommentFilter = CommentFilter;
 
 /**
  * Abstract base class for filters that can get hits
- * @param {string} text
- *   see Filter()
- * @param {string} [domains]
- *   Domains that the filter is restricted to separated by domainSeparator
- *   e.g. "foo.com|bar.com|~baz.com"
- * @constructor
- * @augments Filter
  */
-function ActiveFilter(text, domains)
+class ActiveFilter extends Filter
 {
-  Filter.call(this, text);
+  /**
+   * @param {string} text
+   *   see Filter()
+   * @param {string} [domains]
+   *   Domains that the filter is restricted to separated by domainSeparator
+   *   e.g. "foo.com|bar.com|~baz.com"
+   */
+  constructor(text, domains)
+  {
+    super(text);
 
-  if (domains)
-    this.domainSource = domains;
-}
-exports.ActiveFilter = ActiveFilter;
-
-ActiveFilter.prototype = extend(Filter, {
-  _disabled: false,
-  _hitCount: 0,
-  _lastHit: 0,
+    if (domains)
+      this.domainSource = domains;
+  }
 
   /**
    * Defines whether the filter is disabled
    * @type {boolean}
    */
   get disabled()
   {
     return this._disabled;
-  },
+  }
   set disabled(value)
   {
     if (value != this._disabled)
     {
       let oldValue = this._disabled;
       this._disabled = value;
       FilterNotifier.triggerListeners("filter.disabled", this, value, oldValue);
     }
     return this._disabled;
-  },
+  }
 
   /**
    * Number of hits on the filter since the last reset
    * @type {number}
    */
   get hitCount()
   {
     return this._hitCount;
-  },
+  }
   set hitCount(value)
   {
     if (value != this._hitCount)
     {
       let oldValue = this._hitCount;
       this._hitCount = value;
       FilterNotifier.triggerListeners("filter.hitCount", this, value, oldValue);
     }
     return this._hitCount;
-  },
+  }
 
   /**
    * Last time the filter had a hit (in milliseconds since the beginning of the
    * epoch)
    * @type {number}
    */
   get lastHit()
   {
     return this._lastHit;
-  },
+  }
   set lastHit(value)
   {
     if (value != this._lastHit)
     {
       let oldValue = this._lastHit;
       this._lastHit = value;
       FilterNotifier.triggerListeners("filter.lastHit", this, value, oldValue);
     }
     return this._lastHit;
-  },
-
-  /**
-   * String that the domains property should be generated from
-   * @type {?string}
-   */
-  domainSource: null,
-
-  /**
-   * Separator character used in domainSource property, must be
-   * overridden by subclasses
-   * @type {string}
-   */
-  domainSeparator: null,
-
-  /**
-   * 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 {?Map.<string,boolean>}
    */
   get domains()
   {
@@ -446,23 +427,17 @@
           domains.set("", !hasIncludes);
       }
 
       this.domainSource = null;
     }
 
     Object.defineProperty(this, "domains", {value: domains, enumerable: true});
     return this.domains;
-  },
-
-  /**
-   * Array containing public keys of websites that this filter should apply to
-   * @type {?string[]}
-   */
-  sitekeys: null,
+  }
 
   /**
    * Checks whether this filter is active on a domain.
    * @param {string} [docDomain] domain name of the document that loads the URL
    * @param {string} [sitekey] public key provided by the document
    * @return {boolean} true in case of the filter being active
    */
   isActiveOnDomain(docDomain, sitekey)
@@ -494,17 +469,17 @@
         return isDomainIncluded;
 
       let nextDot = docDomain.indexOf(".");
       if (nextDot < 0)
         break;
       docDomain = docDomain.substr(nextDot + 1);
     }
     return this.domains.get("");
-  },
+  }
 
   /**
    * Checks whether this filter is active only on a domain and its subdomains.
    * @param {string} docDomain
    * @return {boolean}
    */
   isActiveOnlyOnDomain(docDomain)
   {
@@ -521,27 +496,27 @@
           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.get(""));
-  },
+  }
 
   /**
    * See Filter.serialize()
    * @inheritdoc
    */
   serialize(buffer)
   {
     if (this._disabled || this._hitCount || this._lastHit)
@@ -550,150 +525,135 @@
       if (this._disabled)
         buffer.push("disabled=true");
       if (this._hitCount)
         buffer.push("hitCount=" + this._hitCount);
       if (this._lastHit)
         buffer.push("lastHit=" + this._lastHit);
     }
   }
+}
+
+exports.ActiveFilter = ActiveFilter;
+
+Object.assign(ActiveFilter.prototype, {
+  _disabled: false,
+  _hitCount: 0,
+  _lastHit: 0
 });
 
 /**
+ * String that the domains property should be generated from
+ * @type {?string}
+ */
+ActiveFilter.prototype.domainSource = null;

[Manish Jethani, 2018/06/09 13:03:32]

Where the instance property is not always assigned (i.e. the value sometimes
must come from the prototype), we add it to the prototype just like before and
include the JSDoc comment above.

+
+/**
+ * Separator character used in domainSource property, must be
+ * overridden by subclasses
+ * @type {string}
+ */
+ActiveFilter.prototype.domainSeparator = null;
+
+/**
+ * Determines whether domainSource is already upper-case,
+ * can be overridden by subclasses.
+ * @type {boolean}
+ */
+ActiveFilter.prototype.domainSourceIsUpperCase = false;
+
+/**
+ * Array containing public keys of websites that this filter should apply to
+ * @type {?string[]}
+ */
+ActiveFilter.prototype.sitekeys = null;
+
+/**
  * Abstract base class for RegExp-based filters
- * @param {string} text see Filter()
- * @param {string} regexpSource
- *   filter part that the regular expression should be build from
- * @param {number} [contentType]
- *   Content types the filter applies to, combination of values from
- *   RegExpFilter.typeMap
- * @param {boolean} [matchCase]
- *   Defines whether the filter should distinguish between lower and upper case
- *   letters
- * @param {string} [domains]
- *   Domains that the filter is restricted to, e.g. "foo.com|bar.com|~baz.com"
- * @param {boolean} [thirdParty]
- *   Defines whether the filter should apply to third-party or first-party
- *   content only
- * @param {string} [sitekeys]
- *   Public keys of websites that this filter should apply to
- * @constructor
- * @augments ActiveFilter
  */
-function RegExpFilter(text, regexpSource, contentType, matchCase, domains,
-                      thirdParty, sitekeys)
+class RegExpFilter extends ActiveFilter
 {
-  ActiveFilter.call(this, text, domains, sitekeys);
-
-  if (contentType != null)
-    this.contentType = contentType;
-  if (matchCase)
-    this.matchCase = matchCase;
-  if (thirdParty != null)
-    this.thirdParty = thirdParty;
-  if (sitekeys != null)
-    this.sitekeySource = sitekeys;
-
-  if (regexpSource.length >= 2 &&
-      regexpSource[0] == "/" &&
-      regexpSource[regexpSource.length - 1] == "/")
+  /**
+   * @param {string} text see Filter()
+   * @param {string} regexpSource
+   *   filter part that the regular expression should be build from
+   * @param {number} [contentType]
+   *   Content types the filter applies to, combination of values from
+   *   RegExpFilter.typeMap
+   * @param {boolean} [matchCase]
+   *   Defines whether the filter should distinguish between lower and upper
+   *   case letters
+   * @param {string} [domains]
+   *   Domains that the filter is restricted to, e.g. "foo.com|bar.com|~baz.com"
+   * @param {boolean} [thirdParty]
+   *   Defines whether the filter should apply to third-party or first-party
+   *   content only
+   * @param {string} [sitekeys]
+   *   Public keys of websites that this filter should apply to
+   */
+  constructor(text, regexpSource, contentType, matchCase, domains, thirdParty,
+              sitekeys)
   {
-    // The filter is a regular expression - convert it immediately to
-    // catch syntax errors
-    let regexp = new RegExp(regexpSource.substr(1, regexpSource.length - 2),
-                            this.matchCase ? "" : "i");
-    Object.defineProperty(this, "regexp", {value: regexp});
-  }
-  else
-  {
-    // No need to convert this filter to regular expression yet, do it on demand
-    this.regexpSource = regexpSource;
-  }
-}
-exports.RegExpFilter = RegExpFilter;
+    super(text, domains, sitekeys);
+
+    if (contentType != null)
+      this.contentType = contentType;
+    if (matchCase)
+      this.matchCase = matchCase;
+    if (thirdParty != null)
+      this.thirdParty = thirdParty;
+    if (sitekeys != null)
+      this.sitekeySource = sitekeys;
 
-RegExpFilter.prototype = extend(ActiveFilter, {
-  /**
-   * @see ActiveFilter.domainSourceIsUpperCase
-   */
-  domainSourceIsUpperCase: true,
+    if (regexpSource.length >= 2 &&
+        regexpSource[0] == "/" &&
+        regexpSource[regexpSource.length - 1] == "/")
+    {
+      // The filter is a regular expression - convert it immediately to
+      // catch syntax errors
+      let regexp = new RegExp(regexpSource.substr(1, regexpSource.length - 2),
+                              this.matchCase ? "" : "i");
+      Object.defineProperty(this, "regexp", {value: regexp});
+    }
+    else
+    {
+      // No need to convert this filter to regular expression yet, do it on
+      // demand
+      this.regexpSource = regexpSource;
+    }
+  }
 
   /**
-   * Number of filters contained, will always be 1 (required to
-   * optimize Matcher).
-   * @type {number}
-   */
-  length: 1,
-
-  /**
-   * @see ActiveFilter.domainSeparator
-   */
-  domainSeparator: "|",
-
-  /**
-   * Expression from which a regular expression should be generated -
-   * for delayed creation of the regexp property
-   * @type {string}
-   */
-  regexpSource: null,
-  /**
    * Regular expression to be used when testing against this filter
    * @type {RegExp}
    */
   get regexp()
   {
     let source = Filter.toRegExp(this.regexpSource);
     let regexp = new RegExp(source, this.matchCase ? "" : "i");
     Object.defineProperty(this, "regexp", {value: regexp});
     this.regexpSource = null;
     return regexp;
-  },
-  /**
-   * Content types the filter applies to, combination of values from
-   * RegExpFilter.typeMap
-   * @type {number}
-   */
-  contentType: 0x7FFFFFFF,
-  /**
-   * Defines whether the filter should distinguish between lower and
-   * upper case letters
-   * @type {boolean}
-   */
-  matchCase: false,
-  /**
-   * Defines whether the filter should apply to third-party or
-   * first-party content only. Can be null (apply to all content).
-   * @type {?boolean}
-   */
-  thirdParty: null,
+  }
 
-  /**
-   * String that the sitekey property should be generated from
-   * @type {?string}
-   */
-  sitekeySource: null,
-
-  /**
-   * @see ActiveFilter.sitekeys
-   */
   get sitekeys()
   {
     let sitekeys = null;
 
     if (this.sitekeySource)
     {
       sitekeys = this.sitekeySource.split("|");
       this.sitekeySource = null;
     }
 
     Object.defineProperty(
       this, "sitekeys", {value: sitekeys, enumerable: true}
     );
     return this.sitekeys;
-  },
+  }
 
   /**
    * Tests whether the URL matches this filter
    * @param {string} location URL to be tested
    * @param {number} typeMask bitmask of content / request types to match
    * @param {string} [docDomain] domain name of the document that loads the URL
    * @param {boolean} [thirdParty] should be true if the URL is a third-party
    *                               request
@@ -705,17 +665,70 @@
     if (this.contentType & typeMask &&
         (this.thirdParty == null || this.thirdParty == thirdParty) &&
         this.isActiveOnDomain(docDomain, sitekey) && this.regexp.test(location))
     {
       return true;
     }
     return false;
   }
-});
+}
+
+exports.RegExpFilter = RegExpFilter;
+
+/**
+ * @see ActiveFilter.domainSourceIsUpperCase
+ */
+RegExpFilter.prototype.domainSourceIsUpperCase = true;
+
+/**
+ * Number of filters contained, will always be 1 (required to
+ * optimize Matcher).
+ * @type {number}
+ */
+RegExpFilter.prototype.length = 1;
+
+/**
+ * @see ActiveFilter.domainSeparator
+ */
+RegExpFilter.prototype.domainSeparator = "|";
+
+/**
+ * Expression from which a regular expression should be generated -
+ * for delayed creation of the regexp property
+ * @type {string}
+ */
+RegExpFilter.prototype.regexpSource = null;
+
+/**
+ * Content types the filter applies to, combination of values from
+ * RegExpFilter.typeMap
+ * @type {number}
+ */
+RegExpFilter.prototype.contentType = 0x7FFFFFFF;
+
+/**
+ * Defines whether the filter should distinguish between lower and
+ * upper case letters
+ * @type {boolean}
+ */
+RegExpFilter.prototype.matchCase = false;
+
+/**
+ * Defines whether the filter should apply to third-party or
+ * first-party content only. Can be null (apply to all content).
+ * @type {?boolean}
+ */
+RegExpFilter.prototype.thirdParty = null;
+
+/**
+ * String that the sitekey property should be generated from
+ * @type {?string}
+ */
+RegExpFilter.prototype.sitekeySource = null;
 
 // Required to optimize Matcher, see also RegExpFilter.prototype.length
 Object.defineProperty(RegExpFilter.prototype, "0", {
   get() { return this; }
 });
 
 /**
  * Creates a RegExp filter from its text representation
@@ -859,72 +872,55 @@
                                         RegExpFilter.typeMap.DOCUMENT |
                                         RegExpFilter.typeMap.ELEMHIDE |
                                         RegExpFilter.typeMap.POPUP |
                                         RegExpFilter.typeMap.GENERICHIDE |
                                         RegExpFilter.typeMap.GENERICBLOCK);
 
 /**
  * Class for blocking filters
- * @param {string} text see Filter()
- * @param {string} regexpSource see RegExpFilter()
- * @param {number} [contentType] see RegExpFilter()
- * @param {boolean} [matchCase] see RegExpFilter()
- * @param {string} [domains] see RegExpFilter()
- * @param {boolean} [thirdParty] see RegExpFilter()
- * @param {string} [sitekeys] see RegExpFilter()
- * @param {boolean} [collapse]
- *   defines whether the filter should collapse blocked content, can be null
- * @param {string} [csp]
- *   Content Security Policy to inject when the filter matches
- * @param {?string} [rewrite]
- *   The (optional) rule specifying how to rewrite the URL. See
- *   BlockingFilter.prototype.rewrite.
- * @constructor
- * @augments RegExpFilter
  */
-function BlockingFilter(text, regexpSource, contentType, matchCase, domains,
-                        thirdParty, sitekeys, collapse, csp, rewrite)
+class BlockingFilter extends RegExpFilter
 {
-  RegExpFilter.call(this, text, regexpSource, contentType, matchCase, domains,
-                    thirdParty, sitekeys);
-
-  if (collapse != null)
-    this.collapse = collapse;
+  /**
+   * @param {string} text see Filter()
+   * @param {string} regexpSource see RegExpFilter()
+   * @param {number} [contentType] see RegExpFilter()
+   * @param {boolean} [matchCase] see RegExpFilter()
+   * @param {string} [domains] see RegExpFilter()
+   * @param {boolean} [thirdParty] see RegExpFilter()
+   * @param {string} [sitekeys] see RegExpFilter()
+   * @param {boolean} [collapse]
+   *   defines whether the filter should collapse blocked content, can be null
+   * @param {string} [csp]
+   *   Content Security Policy to inject when the filter matches
+   * @param {?string} [rewrite]
+   *   The (optional) rule specifying how to rewrite the URL. See
+   *   BlockingFilter.prototype.rewrite.
+   */
+  constructor(text, regexpSource, contentType, matchCase, domains, thirdParty,
+              sitekeys, collapse, csp, rewrite)
+  {
+    super(text, regexpSource, contentType, matchCase, domains, thirdParty,
+          sitekeys);
 
-  if (csp != null)
-    this.csp = csp;
+    if (collapse != null)
+      this.collapse = collapse;
 
-  if (rewrite != null)
-    this.rewrite = rewrite;
-}
-exports.BlockingFilter = BlockingFilter;
-
-BlockingFilter.prototype = extend(RegExpFilter, {
-  type: "blocking",
+    if (csp != null)
+      this.csp = csp;
 
-  /**
-   * Defines whether the filter should collapse blocked content.
-   * Can be null (use the global preference).
-   * @type {?boolean}
-   */
-  collapse: null,
+    if (rewrite != null)
+      this.rewrite = rewrite;
+  }
 
-  /**
-   * Content Security Policy to inject for matching requests.
-   * @type {?string}
-   */
-  csp: null,
-
-  /**
-   * The rule specifying how to rewrite the URL.
-   * The syntax is similar to the one of String.prototype.replace().
-   * @type {?string}
-   */
-  rewrite: null,
+  get type()
+  {
+    return "blocking";
+  }
 
   /**
    * Rewrites an URL.
    * @param {string} url the URL to rewrite
    * @return {string} the rewritten URL, or the original in case of failure
    */
   rewriteUrl(url)
   {
@@ -935,73 +931,100 @@
         return rewrittenUrl.href;
     }
     catch (e)
     {
     }
 
     return url;
   }
-});
+}
+
+exports.BlockingFilter = BlockingFilter;
+
+/**
+ * Defines whether the filter should collapse blocked content.
+ * Can be null (use the global preference).
+ * @type {?boolean}
+ */
+BlockingFilter.prototype.collapse = null;
+
+/**
+ * Content Security Policy to inject for matching requests.
+ * @type {?string}
+ */
+BlockingFilter.prototype.csp = null;
+
+/**
+ * The rule specifying how to rewrite the URL.
+ * The syntax is similar to the one of String.prototype.replace().
+ * @type {?string}
+ */
+BlockingFilter.prototype.rewrite = null;
 
 /**
  * Class for whitelist filters
- * @param {string} text see Filter()
- * @param {string} regexpSource see RegExpFilter()
- * @param {number} [contentType] see RegExpFilter()
- * @param {boolean} [matchCase] see RegExpFilter()
- * @param {string} [domains] see RegExpFilter()
- * @param {boolean} [thirdParty] see RegExpFilter()
- * @param {string} [sitekeys] see RegExpFilter()
- * @constructor
- * @augments RegExpFilter
  */
-function WhitelistFilter(text, regexpSource, contentType, matchCase, domains,
-                         thirdParty, sitekeys)
+class WhitelistFilter extends RegExpFilter
 {
-  RegExpFilter.call(this, text, regexpSource, contentType, matchCase, domains,
-                    thirdParty, sitekeys);
+  /**
+   * @param {string} text see Filter()
+   * @param {string} regexpSource see RegExpFilter()
+   * @param {number} [contentType] see RegExpFilter()
+   * @param {boolean} [matchCase] see RegExpFilter()
+   * @param {string} [domains] see RegExpFilter()
+   * @param {boolean} [thirdParty] see RegExpFilter()
+   * @param {string} [sitekeys] see RegExpFilter()
+   */
+  constructor(text, regexpSource, contentType, matchCase, domains, thirdParty,
+              sitekeys)
+  {
+    super(text, regexpSource, contentType, matchCase, domains, thirdParty,
+          sitekeys);
+  }
+
+  get type()
+  {
+    return "whitelist";
+  }
 }
+
 exports.WhitelistFilter = WhitelistFilter;
 
-WhitelistFilter.prototype = extend(RegExpFilter, {
-  type: "whitelist"
-});
-
 /**
  * Base class for element hiding filters
- * @param {string} text see Filter()
- * @param {string} [domains] Host names or domains the filter should be
- *                           restricted to
- * @param {string} selector   CSS selector for the HTML elements that should be
- *                            hidden
- * @constructor
- * @augments ActiveFilter
  */
-function ElemHideBase(text, domains, selector)
+class ElemHideBase extends ActiveFilter
 {
-  ActiveFilter.call(this, text, domains || null);
+  /**
+   * @param {string} text see Filter()
+   * @param {string} [domains] Host names or domains the filter should be
+   *                           restricted to
+   * @param {string} selector   CSS selector for the HTML elements that should
+   *                            be hidden
+   */
+  constructor(text, domains, selector)
+  {
+    super(text, domains || null);
 
-  // Braces are being escaped to prevent CSS rule injection.
-  this.selector = selector.replace("{", "\\7B ").replace("}", "\\7D ");
+    /**
+     * CSS selector for the HTML elements that should be hidden
+     * @type {string}
+     */
+    // Braces are being escaped to prevent CSS rule injection.
+    this.selector = selector.replace("{", "\\7B ").replace("}", "\\7D ");
+  }
 }
+
 exports.ElemHideBase = ElemHideBase;
 
-ElemHideBase.prototype = extend(ActiveFilter, {
-  /**
-   * @see ActiveFilter.domainSeparator
-   */
-  domainSeparator: ",",
-
-  /**
-   * CSS selector for the HTML elements that should be hidden
-   * @type {string}
-   */
-  selector: null
-});
+/**
+ * @see ActiveFilter.domainSeparator
+ */
+ElemHideBase.prototype.domainSeparator = ",";
 
 /**
  * Creates an element hiding filter from a pre-parsed text representation
  *
  * @param {string} text         same as in Filter()
  * @param {string} [domains]
  *   domains part of the text representation
  * @param {string} [type]
@@ -1031,59 +1054,74 @@
     return new ElemHideEmulationFilter(text, domains, selector);
   }
 
   return new ElemHideFilter(text, domains, selector);
 };
 
 /**
  * Class for element hiding filters
- * @param {string} text see Filter()
- * @param {string} [domains]  see ElemHideBase()
- * @param {string} selector see ElemHideBase()
- * @constructor
- * @augments ElemHideBase
  */
-function ElemHideFilter(text, domains, selector)
+class ElemHideFilter extends ElemHideBase
 {
-  ElemHideBase.call(this, text, domains, selector);
-}
-exports.ElemHideFilter = ElemHideFilter;
+  /**
+   * @param {string} text see Filter()
+   * @param {string} [domains]  see ElemHideBase()
+   * @param {string} selector see ElemHideBase()
+   */
+  constructor(text, domains, selector)
+  {
+    super(text, domains, selector);
+  }
 
-ElemHideFilter.prototype = extend(ElemHideBase, {
-  type: "elemhide"
-});
+  get type()
+  {
+    return "elemhide";
+  }
+}
+
+exports.ElemHideFilter = ElemHideFilter;
 
 /**
  * Class for element hiding exceptions
- * @param {string} text see Filter()
- * @param {string} [domains]  see ElemHideBase()
- * @param {string} selector see ElemHideBase()
- * @constructor
- * @augments ElemHideBase
  */
-function ElemHideException(text, domains, selector)
+class ElemHideException extends ElemHideBase
 {
-  ElemHideBase.call(this, text, domains, selector);
-}
-exports.ElemHideException = ElemHideException;
+  /**
+   * @param {string} text see Filter()
+   * @param {string} [domains]  see ElemHideBase()
+   * @param {string} selector see ElemHideBase()
+   */
+  constructor(text, domains, selector)
+  {
+    super(text, domains, selector);
+  }
 
-ElemHideException.prototype = extend(ElemHideBase, {
-  type: "elemhideexception"
-});
+  get type()
+  {
+    return "elemhideexception";
+  }
+}
+
+exports.ElemHideException = ElemHideException;
 
 /**
  * Class for element hiding emulation filters
- * @param {string} text           see Filter()
- * @param {string} domains        see ElemHideBase()
- * @param {string} selector       see ElemHideBase()
- * @constructor
- * @augments ElemHideBase
  */
-function ElemHideEmulationFilter(text, domains, selector)
+class ElemHideEmulationFilter extends ElemHideBase
 {
-  ElemHideBase.call(this, text, domains, selector);
-}
-exports.ElemHideEmulationFilter = ElemHideEmulationFilter;
+  /**
+   * @param {string} text           see Filter()
+   * @param {string} domains        see ElemHideBase()
+   * @param {string} selector       see ElemHideBase()
+   */
+  constructor(text, domains, selector)
+  {
+    super(text, domains, selector);
+  }
 
-ElemHideEmulationFilter.prototype = extend(ElemHideBase, {
-  type: "elemhideemulation"
-});
+  get type()
+  {
+    return "elemhideemulation";
+  }
+}
+
+exports.ElemHideEmulationFilter = ElemHideEmulationFilter;