This app demos an editor with language smarts (for JavaScript) by hosting the Monaco widget with an LSP server implemented via tower-lsp and tree-sitter. Everything is compiled to WASM and run client-side directly in the browser; there are no separate sever-side processes or web workers used by the app code. (Monaco itself does use web workers, however).
features: ⇧⌘O (macos) or ⇧⌃O (windows) opens symbol view; the syntax area shows the JavaScript syntax tree (green for valid; red for errors) parsed from editor