JavaScript & TypeScript language server to add JS/TS support to editors and other tools that use the Language Server Protocol (LSP)
TypeScript JavaScript
Latest commit 7de786d Feb 22, 2017 @felixfbecker felixfbecker Fix formatting

JavaScript/TypeScript language server

This is a language server for JavaScript and TypeScript that adheres to the Language Server Protocol (LSP). It uses TypeScript's LanguageService to perform source code analysis.

Getting started

  1. yarn install
  2. node_modules/.bin/tsc
  3. node lib/language-server.js

To try it in Visual Studio Code, install the vscode-client extension and then open up a .ts file.


Run node_modules/.bin/tsc --watch.


Run yarn test.

Command line arguments

  • -p, --port specifies port to use, default one is 2089
  • -s, --strict enables strict mode where server expects all files to be receives in didOpen notification requests
  • -c, --cluster specifies number of concurrent cluster workers (defaults to number of CPUs)
  • -t, --trace enables printing of all incoming and outgoing messages
  • -l, --logfile specifies additional log file to print all messages to

Supported LSP requests


In strict mode we expect rootPath to be equal file:/// while in non-strict mode VSCode usually sends absolute file URL. In both modes does not track existence of calling process.


Implementation closes underlying communication channel


Does nothing opposite to LSP specification that expects server to exit





Introduces limit parameter to limit number of symbols to return

Differences from LSP protocol specification

In strict mode LSP server does not touch underlying file system, instead it uses addition to LSP protocol to fetch information about workspace structure and files content by sending proprietary fs/... requests back to the caller (fs/readDir, fs/readFile) and keeping results in memory.

Known issues

  • You need to disable VSCode's built-in TypeScript support to avoid weird conflicts on TypeScript files (double hover tooltips, etc.). There's a hacky way to do this: add the setting {"typescript.tsdk": "/dev/null"} to your VSCode user or workspace settings.