@babel/cli

Babel comes with a built-in CLI which can be used to compile files from the command line.

In addition, various entry point scripts live in the top-level package at @babel/cli/bin. There is a shell-executable utility script, babel-external-helpers.js, and the main Babel cli script, babel.js.

Install

While you can install Babel CLI globally on your machine, it's much betterto install it locally project by project.

There are two primary reasons for this.

  • Different projects on the same machine can depend on different versions ofBabel allowing you to update them individually.
  • Not having an implicit dependency on the environment you are working inmakes your project far more portable and easier to setup.We can install Babel CLI locally by running:
  1. npm install --save-dev @babel/core @babel/cli

Note: If you do not have a package.json, create one before installing. This will ensure proper interaction with the npx command.

After that finishes installing, your package.json file should include:

  1. {
  2.   "devDependencies": {
  3. +   "@babel/cli": "^7.0.0",
  4. +   "@babel/core": "^7.0.0"
  5.   }
  6. }

Usage

  1. babel script.js

Note: These instructions use the excellent npx command to run the locally installed executables. You can drop it inside of an npm run script or you may instead execute with the relative path instead. ./node_modules/.bin/babel

Compile Files

Compile the file script.js and output to stdout.

  1. npx babel script.js
  2. # output...

If you would like to output to a file you may use —out-file or -o.

  1. npx babel script.js --out-file script-compiled.js

To compile a file every time that you change it, use the —watch or -w option:

  1. npx babel script.js --watch --out-file script-compiled.js

Compile with Source Maps

If you would then like to add a source map file you can use—source-maps or -s. Learn more about source maps.

  1. npx babel script.js --out-file script-compiled.js --source-maps

Or, if you'd rather have inline source maps, use —source-maps inline instead.

  1. npx babel script.js --out-file script-compiled.js --source-maps inline

Compile Directories

Compile the entire src directory and output it to the lib directory by using either —out-dir or -d. This doesn't overwrite any other files or directories in lib.

  1. npx babel src --out-dir lib

Compile the entire src directory and output it as a single concatenated file.

  1. npx babel src --out-file script-compiled.js

Ignore files

Ignore spec and test files

  1. npx babel src --out-dir lib --ignore "src/**/*.spec.js","src/**/*.test.js"

Copy files

Copy files that will not be compiled

  1. npx babel src --out-dir lib --copy-files

Piping Files

Pipe a file in via stdin and output it to script-compiled.js

  1. npx babel --out-file script-compiled.js < script.js

Using Plugins

Use the —plugins option to specify plugins to use in compilation

  1. npx babel script.js --out-file script-compiled.js --plugins=@babel/proposal-class-properties,@babel/transform-modules-amd

Using Presets

Use the —presets option to specify presets to use in compilation

  1. npx babel script.js --out-file script-compiled.js --presets=@babel/preset-env,@babel/flow

Ignoring .babelrc.json

Ignore the configuration from the project's .babelrc.json file and use the cli options e.g. for a custom build

  1. npx babel --no-babelrc script.js --out-file script-compiled.js --presets=es2015,react

Set File Extensions

By default, Babel will override the extension of the transpiled file and use .js instead.

To preserve the original file extension you can pass the —keep-file-extension.

You can also control what file extension is used with —out-file-extension .example-extension e.g. babel src/ lib/ —out-file-extension .mjs.

Note that —keep-file-extension and —out-file-extension cannot be used together.

Advanced Usage

There are many more options available, see options, babel —help and other sections for more information.