Type-checked JavaScript in Neovim

Enable a TypeScript language server

With nvim-lspconfig installed (it provides the server definitions), one line in init.lua starts ts_ls for JavaScript and TypeScript buffers. Install the server first: nvim-lspconfig's ts_ls config gives npm install -g typescript typescript-language-server, and its vtsls config gives npm install -g @vtsls/language-server.

-- Neovim 0.11+, with nvim-lspconfig installed for its server definitions
vim.lsp.enable('ts_ls')

Use the project's TypeScript

The version matters because each TypeScript release adds and changes checks; the editor should run the version in your project's node_modules, which is what npm run lint runs. typescript-language-server reports where its TypeScript came from (the workspace, a configured tsserver.path, or its bundled copy), and the ts_ls config starts a project-local typescript-language-server from node_modules/.bin when there is one.

vtsls uses the TypeScript it bundles unless you set vtsls.autoUseWorkspaceTsdk, per its README:

vim.lsp.config('vtsls', {
  settings = {
    -- use node_modules/typescript instead of the copy vtsls ships with
    vtsls = { autoUseWorkspaceTsdk = true },
  },
})
vim.lsp.enable('vtsls')

How the config is found

nvim-lspconfig decides the workspace root from lockfiles and .git, not from jsconfig.json. That is only the LSP workspace: inside it, TypeScript's server still looks for the nearest jsconfig.json or tsconfig.json above each file, so a project with several configs is checked with the right one per file.

What differs from tsc

Neovim shows the diagnostics for the buffers you open, through vim.diagnostic (configure how with vim.diagnostic.config()). Servers also pass on TypeScript's suggestions, such as unused names when noUnusedLocals is off and names marked @deprecated; tsc never prints those. Quick fixes come through code actions (the default gra mapping).

Make sure it matches tsc

Run npm run lint (or npx tsc -p jsconfig.json --pretty false) in a terminal, open one of the files it lists, and compare the codes. Errors in files you have not opened appear only in that output.