The compiler for writing next generation JavaScript.

Babel is a community-driven tool that helps you write code in the latest version of JavaScript.

When your supported environments don't support certain features natively, Babel will help you compile those features down to a supported version.

In

// ES2015 arrow function
[1, 2, 3].map((n) => n + 1);

Out

[1, 2, 3].map(function(n) {
  return n + 1;
});

Try it out at our REPL and follow us at @babeljs.

• FAQ
• Packages
  • Core Packages
  • Other
  • Presets
  • Plugins
    • Transform Plugins
    • Syntax Plugins
  • Misc Packages
• Team
• License

Check out our website: babeljs.io

For questions and support please visit our discussion forum, sign up for our Slack community, or StackOverflow.

Bugs and feature requests can be posted at https://github.com/babel/babel/issues.

We've moved our issues from phabricator back to github issues!

Former phabricator issue URLs now automatically redirect to their corresponding Github issue:

https://phabricator.babeljs.io/T2168 mostly corresponds to babel#2168.

For documentation and website issues please visit the babel/website repo.

Check out our CONTRIBUTING.md. If you have already joined Slack, join our #development channel!

You can also start by checking out the issues with the help-wanted label.

Our discussions/notes/roadmap: babel/notes Our progress on TC39 proposals: babel/proposals

The Babel repo is managed as a monorepo that is composed of many npm packages.

Package	Version	Dependencies
babel-core
babylon
babel-traverse
babel-generator

babel-core is the Babel compiler itself; it exposes the babel.transform method, where transformedCode = transform(src).code.

The compiler can be broken down into 3 parts:

• The parser: babylon (moved to a separate repo and versioned independently)
• The transformer[s]: All the plugins/presets
  • These all use babel-traverse to traverse through the AST
• The generator: babel-generator

The flow goes like this:

input string -> babylon parser -> AST -> transformer[s] -> AST -> babel-generator -> output string

Check out the babel-handbook for more information on this.

Package	Version	Dependencies
babel-cli
babel-types
babel-polyfill
babel-runtime
babel-register
babel-template
babel-helpers
babel-code-frame

• babel-cli is the CLI tool that runs babel-core and helps with outputting to a directory, a file, stdout and more (also includes babel-node). Check out the docs.
• babel-types is used to validate, build and change AST nodes.
• babel-polyfill is literally a wrapper around core-js and regenerator-runtime. Check out the docs.
• babel-runtime is similar to the polyfill except that it doesn't modify the global scope and is to be used with babel-plugin-transform-runtime (usually in library/plugin code). Check out the docs.
• babel-register is a way to automatically compile files with Babel on the fly by binding to Node.js require. Check out the docs.
• babel-template is a helper function that allows constructing AST nodes from a string presentation of the code; this eliminates the tedium of using babel-types for building AST nodes.
• babel-helpers is a set of pre-made babel-template functions that are used in some Babel plugins.
• babel-code-frame is a standalone package used to generate errors that print the source code and point to error locations.

After Babel 6, the default transforms were removed; if you don't specify any plugins/presets, Babel will just return the original source code.

The transformer[s] used in Babel are the independent pieces of code that transform specific things. For example: the es2015-arrow-functions transform specifically changes arrow functions into regular functions. A preset is simply an array of plugins that make it easier to run a whole a set of transforms without specifying each one manually.

Package	Version	Dependencies	Description
babel-preset-env			automatically determines plugins and polyfills you need based on your supported environments

You can find community maintained presets on npm

Plugins are the heart of Babel and what make it work.

You can find community plugins on npm.

There are many kinds of plugins: ones that convert ES6/ES2015 to ES5, transform to ES3, minification, JSX, flow, experimental features, and more. Check out our website for more.

These just enable the transform plugins to be able to parse certain features (the transform plugins already include the syntax plugins so you don't need both): babel-plugin-syntax-x. Check out our website for more.

These are mostly for internal use in various plugins: babel-helper-x.

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