I upgraded the PhpED 18, and it seems to me, the new syntax and features in JavaScript is not implemented.

For example let keyword.

http:// es6-features.org/#BlockScopedVariables

Is there a way to fix it myself? Possibly the expansion of the library?

Sorry, ECMAScript 6 is not supported. Adding support for such things requires a lot of work. There is nothing you can do.

OK., i understand.

Any plans in the future, or in following version for this support? Including better CSS3 syntax check?

yes, sure. We revisit all the features and tight them up

That's clear, it's a must have, but we can't afford developing ES[6,8] parsers from scratches -- it would take tremendous time with very marginal benefit -- although it lies very close, support for JS is not our primary goal.
Tried to find a grammar (something like yacc, lemon or bison would work great for us), but didn't find anything suitable. Would highly appreciate if you find anything suitable.

Thanks, I'll check that. This file https://bitbucket.org/skoppe/es6-grammar/src/57e0c27267a644f83184a8e38780d37d77299fdd/source/es6/grammar-generator.d?at=master&fileviewer=file-view-default looks like tokenizer (lexer) and parser.
What's about ES8?

I actually agree with dmitri.

I'd much rather see NuSphere fix existing bugs and annoyances than worry about JS syntax highlighting.

But will you, dmitri, ever fix those?

I'm not sure what "bugs" you encounter. If you have something you can reproduce, please report to support and make sure that they reproduced it too. In this case we'll fix the problem fast.

As of ES6/ES8, my understanding is that this is more about detected syntax errors.
They can be turned off. Open View->Tabs->Problems window, right click -> Filter -> add *.js to Hide Files input.
That's a temporary solution, of course and it won't hide red underscores and red balloons on the right. That's temporary until we get ES6/8 supported.

I am not sure how intertwined the code collapsing is with the JavaScript parser, but making it work in ES6 cases would make it's support much more usable.

Some examples: