Edit

@babel/preset-stage-1

As of Babel v7, all of the stage-x presets have been deprecated. Check the blog post for more information.

For a more automatic migration, we have updated babel-upgrade to do this for you (you can run npx babel-upgrade).

If you want the same configuration as before:

{
  plugins: [
    // Stage 1
    "@babel/plugin-proposal-export-default-from",
    "@babel/plugin-proposal-logical-assignment-operators",
    ["@babel/plugin-proposal-optional-chaining", { loose: false }],
    ["@babel/plugin-proposal-pipeline-operator", { proposal: "minimal" }],
    ["@babel/plugin-proposal-nullish-coalescing-operator", { loose: false }],
    "@babel/plugin-proposal-do-expressions",

    // Stage 2
    ["@babel/plugin-proposal-decorators", { legacy: true }],
    "@babel/plugin-proposal-function-sent",
    "@babel/plugin-proposal-export-namespace-from",
    "@babel/plugin-proposal-numeric-separator",
    "@babel/plugin-proposal-throw-expressions",

    // Stage 3
    "@babel/plugin-syntax-dynamic-import",
    "@babel/plugin-syntax-import-meta",
    ["@babel/plugin-proposal-class-properties", { loose: false }],
    "@babel/plugin-proposal-json-strings",
  ],
}

If you're using the same configuration across many separate projects, keep in mind that you can also create your own custom presets with whichever plugins and presets you're looking to use.

module.exports = function() {
  return {
    plugins: [
      require("@babel/plugin-syntax-dynamic-import"),
      [require("@babel/plugin-proposal-decorators"), { legacy: true }],
      [require("@babel/plugin-proposal-class-properties"), { loose: false }],
    ],
    presets: [
      // ...
    ],
  };
};

The gist of Stage 1 is:

Stage 1: proposal

What is it? A formal proposal for the feature.

What’s required? A so-called champion must be identified who is responsible for the proposal. Either the champion or a co-champion must be a member of TC39 (source). The problem solved by the proposal must be described in prose. The solution must be described via examples, an API and a discussion of semantics and algorithms. Lastly, potential obstacles for the proposal must be identified, such as interactions with other features and implementation challenges. Implementation-wise, polyfills and demos are needed.

What’s next? By accepting a proposal for stage 1, TC39 declares its willingness to examine, discuss and contribute to the proposal. Going forward, major changes to the proposal are expected

Install

npm install --save-dev @babel/preset-stage-1

Usage

Via .babelrc (Recommended)

.babelrc

{
  "presets": ["@babel/preset-stage-1"]
}

Via CLI

babel script.js --presets @babel/preset-stage-1

Via Node API

require("@babel/core").transform("code", {
  presets: ["@babel/preset-stage-1"],
});

Options

loose

boolean, defaults to false.

Enable "loose" transformations for any plugins in this preset that allow them.

useBuiltIns

boolean, defaults to false.

Will use the native built-in instead of trying to polyfill behavior for any plugins that require one.

decoratorsLegacy

boolean, defaults to false.

Use the legacy (stage 1) decorators syntax and behavior.

References

• Chapter "The TC39 process for ECMAScript features" in "Exploring ES2016 and ES2017" by Axel Rauschmayer