ts-node-dev

ts-node-dev is a CLI that combines ts-node’s on-the-fly TypeScript compilation with nodemon-style file watching and process restarting, while reusing the TypeScript compiler instance across restarts so type-checking isn’t redone from scratch on every change. Running ts-node-dev (or its tsnd alias) in place of ts-node gives a fast development loop for Node.js TypeScript apps.

It supports options like --respawn to keep the watcher alive after a fatal error, --deps to also watch changed dependencies, --transpile-only to skip type-checking for even faster restarts, and standard ts-node compiler flags, making it a common dev script dependency in Node/TypeScript projects before native watch modes became widespread.

What You Get

• A ts-node-dev/tsnd CLI binary that wraps ts-node with file-watching and automatic process restarts
• A cached TypeScript compiler instance shared across restarts, avoiding a full recompile/type-check on every file change
• Flags like --respawn (keep watching after a crash), --deps (watch changed dependencies too), and --transpile-only (skip type-checking for faster restarts)
• Compatibility with standard ts-node/tsconfig.json compiler options, so existing TypeScript configuration is respected

Common Use Cases

• Running a Node.js/Express/API server in development with automatic restarts on source file changes
• Speeding up local iteration on TypeScript backend code compared to a plain ts-node + nodemon combination
• Watching both application source and its local dependencies (via --deps) in a monorepo-style backend setup
• Keeping a dev server alive across uncaught exceptions during active development via --respawn

Under The Hood

Architecture — The CLI entry point (src/bin.ts) parses arguments via minimist and spawns a wrapped Node process (src/wrap.ts) that installs a ts-node-based require hook (src/child-require-hook.ts, src/hook.ts) so TypeScript files are compiled on demand; a chokidar-backed watcher (referenced from src/index.ts) tracks file changes and triggers tree-kill-based process restarts communicated over src/ipc.ts, while src/compiler.ts caches the underlying TypeScript program across restarts to avoid full recompilation. Tech Stack — Node.js/TypeScript CLI built on ts-node for compilation, chokidar for cross-platform file watching, resolve/tsconfig for module and config resolution, tree-kill for reliably terminating child process trees, and dynamic-dedupe to avoid duplicate module instances across restarts. Code Quality — The src/ directory (~1,480 lines across 14 focused modules) separates concerns cleanly (watching, compiling, IPC, logging, resolving), and test/tsnd.test.ts plus a test/fixture directory exercise the CLI end-to-end with Mocha; however the GitHub repository is now archived with no commits since 2024, meaning newer TypeScript/Node versions receive no further compatibility fixes. API Design — Usage is a drop-in CLI replacement for ts-node (ts-node-dev ./src/index.ts instead of ts-node ./src/index.ts), requiring no code changes and only a handful of documented flags, which kept its adoption curve low even as the project stopped receiving updates.