babel-watch

7.8.1 verified Sat Apr 25 auth: no javascript

A fast file watcher and restarter for babel-node apps. Instead of restarting babel-node on each change (which is slow), it runs babel transpilation once in a master process and spawns a plain node child with the transpiled code. Current stable version is 7.8.1, with a maintenance release cadence. Key differentiators: autowatch (automatically watches files as they are required), faster restarts than nodemon+babel-node, and supports Babel 7.

Common errors

error babel-watch: error: unknown option `--config-file' ↓

cause Using --config-file with babel-watch versions older than 7.5.0 which do not support that option.

fix

Update babel-watch to v7.5.0 or later: npm install babel-watch@latest

error Error: Cannot find module '@babel/core' ↓

cause @babel/core is a peer dependency of babel-watch and must be installed separately.

fix

Install @babel/core: npm install --save-dev @babel/core

error babel-watch: FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory ↓

cause The process ran out of memory due to large files or circular requires causing infinite loops.

fix

Increase Node memory limit with --max_old_space_size, or exclude unnecessary directories with --ignore.

error (node:12345) [DEP0005] DeprecationWarning: ... ↓

cause Using deprecated debug options (-d or -B).

fix

Use --inspect or --inspect-brk instead.

error Error: listen EADDRINUSE :::9229 ↓

cause Another process is already using the inspector port when using --inspect without a custom port.

fix

Specify a different port with --inspect 0.0.0.0:9230

Warnings

breaking babel-watch v7 requires Node >= 8 and @babel/core ^7.0.0. It will not work with older Node versions or Babel 6. ↓

fix Update Node to >=8 and install @babel/core@^7.

gotcha When using --ignore, node_modules are ignored by default. If you specify a custom --ignore, you must include node_modules explicitly if you still want to ignore it. ↓

fix Use --ignore 'node_modules' along with other patterns, e.g., --ignore 'node_modules,dist'.

gotcha The --inspect option's address must be specified as a separate argument when using = syntax may cause issues. ↓

fix Use --inspect 0.0.0.0:9229 instead of --inspect=0.0.0.0:9229.

deprecated The -d and -B debug options are deprecated; use --inspect or --inspect-brk instead. ↓

fix Replace -d with --inspect and -B with --inspect-brk.

gotcha Autowatch may ignore files in node_modules by default but may still watch them if they are required. Use -x to exclude additional directories. ↓

fix Pass -x node_modules to exclude node_modules from autowatch.

Install

npm install babel-watch

yarn add babel-watch

pnpm add babel-watch

Quickstart

Installs babel-watch as a dev dependency and creates an npm script to run it with a source file.

{
  "scripts": {
    "start": "babel-watch src/main.js"
  }
}

# Then run:
npm start