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

lib/filterClasses.js

Index: lib/filterClasses.js
diff --git a/lib/filterClasses.js b/lib/filterClasses.js
index 626eabad9538553550f08df724b14fbd077cd08b..504cd4b84503152459684997f83c5298947758b1 100644
--- a/lib/filterClasses.js
+++ b/lib/filterClasses.js
@@ -81,7 +81,7 @@ Filter.prototype =
  * Cache for known filters, maps string representation to filter objects.
  * @type {Object}
  */
-Filter.knownFilters = Object.create(null);
+Filter.knownFilters = new Map();
 
 /**
  * Regular expression that element hiding filters should match
@@ -108,8 +108,8 @@ Filter.optionsRegExp = /\$(~?[\w-]+(?:=[^,\s]+)?(?:,~?[\w-]+(?:=[^,\s]+)?)*)$/;
  */
 Filter.fromText = function(text)
 {
-  if (text in Filter.knownFilters)
-    return Filter.knownFilters[text];
+  if (Filter.knownFilters.has(text))
+    return Filter.knownFilters.get(text);

[Wladimir Palant, 2017/09/20 08:59:10]

It makes little sense to have two calls here. You can call .get() directly and
return if you get a result.

[sergei, 2017/09/20 09:22:40]

I also thought about it because there are no `undefined` values stored in this
object, but decided to leave it as it was before.
Fixed.

 
   let ret;
   let match = (text.includes("#") ? Filter.elemhideRegExp.exec(text) : null);
@@ -136,7 +136,7 @@ Filter.fromText = function(text)
   else
     ret = RegExpFilter.fromText(text);
 
-  Filter.knownFilters[ret.text] = ret;
+  Filter.knownFilters.set(ret.text, ret);
   return ret;
 };