js2-mode was the coolest major mode for Emacs back in the day. The js2 parser is primitive, non-incremental and language-specific.
semantic-mode almost, a-a-a-lmost did something similar (mostly based on LR incremental parsing) but was Emacs-only and never gained enough traction.
Tree-sitter is decades ahead of both. It's hard to compare js2 to a modern GLR incremental parser generator of Tree-sitter. I am not even talking about the size of the community building grammars useful in all the editors out there.
semantic-mode almost, a-a-a-lmost did something similar (mostly based on LR incremental parsing) but was Emacs-only and never gained enough traction.
Tree-sitter is decades ahead of both. It's hard to compare js2 to a modern GLR incremental parser generator of Tree-sitter. I am not even talking about the size of the community building grammars useful in all the editors out there.