Use JS Map instead of Object

[sergz]

Background

I was profiling memory usage of current adblockpluscore a little bit and discovered that after the changes described below the size of RSS is 10-15 MBs less for EasyList+AA, in particular instead of 80.+ MB originally, it's 70.- MBs with the changes (it's a memory usage of a special tests, not all functionality is there). Each change saves merely a few hundreds of KBs or a couple of MBs but in total it's a noticeable result.

I have also tried to change some other Objects which are used as containers to JS Map but it had not helped, so only these changes have a positive effect, at least in my tests.

What to change

Make to be Map:

• Filter.knownFilters
• Filter property domains after lazy evaluation
• Matcher property filterByKeyword
• Matcher property keywordByFilter
• in elemHide.js
  • global keyByFilter
  • global filtersByDomain
  • filters which are stored in filtersByDomain

Integration notes

Please ensure in the dependent projects that the objects mentioned above are treated in accordance with the changes. In particular, the type of following objects changed from Object to Map:

• Filter.knownFilters
• domains property of Filter objects
• Matcher properties filterByKeyword and keywordByFilter
• global (module scoped) filtersByDomain and its values in elemHide.js
• global (module scoped) keyByFilter in elemHide.js

[abpbot]

Some commits referencing this issue have landed:

• ​Issue 5735 - Use JS Map instead of Object for Filter.knownFilters
• ​Issue 5735 - Use JS Map instead of Object for property domains of Filter objects
• ​Issue 5735 - Use JS Map instead of Object for global filtersByDomain in elemHide.js
• ​Issue 5735 - Use JS Map instead of Object for filters which are stored in filtersByDomain in elemHide.js
• ​Issue 5735 - Use JS Map instead of Object for global keyByFilter in elemHide.js
• ​Issue 5735 - Use JS Map instead of Object for matcher properties filterByKeyword and keywordByFilter

[kzar]

(Also see the discussion in #3095.)