Babel is a parser and transpiler for ECMAScript 2015 syntax and beyond, which enables some upcoming JavaScript syntax features to be used in today's browsers and runtimes.

Meteor's Babel support consists of the following core packages:

• babel-compiler - Exposes the Babel API on the symbol Babel. For example, Babel.compile(source, options).

• babel-runtime - Meteor versions of the external helpers used by Babel-generated code. Meteor's core packages must run on IE 8 without polyfills, so these helpers cannot assume the existence of Object.defineProperty, Object.freeze, and so on.

Babel API

The babel-compiler package exports the Babel symbol, which exposes functionality provided by the meteor-babel NPM package, which is in turn implmented using the babel-core NPM package. Note that you can only use the babel-compiler package on the server.

Example:

var babelOptions = Babel.getDefaultOptions();

// Modify the default options, if necessary:
babelOptions.whitelist = [
  "es6.blockScoping", // For `let`
  "es6.arrowFunctions" // For `=>`
];

var result = Babel.compile(
  "let square = (x) => x*x;",
  babelOptions
);

// result.code will be something like
// "var square = function (x) {\n  return x * x;\n};"

Use Babel.compile(source) to transpile code using a set of default options that work well for Meteor code.

Resources:

• API docs
• List of transformers