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Henry Zhu 1196ec1e38 add loose/useBuiltIns option to stage presets, use it, opt babylon build (#6733 )

* add loose, useBuiltIns options to presets + use loose class properties

* whitelist helpers for babylon

* use transform-for-of-as-array in babylon

2017-11-03 14:22:06 -04:00

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@babel/preset-stage-2

Babel preset for stage 2 plugins.

The gist of Stage 2 is:

Stage 2: draft

What is it? A first version of what will be in the specification. At this point, an eventual inclusion of the feature in the standard is likely.

What’s required? The proposal must now additionally have a formal description of the syntax and semantics of the feature (using the formal language of the ECMAScript specification). The description should be as complete as possible, but can contain todos and placeholders. Two experimental implementations of the feature are needed, but one of them can be in a transpiler such as Babel.

What’s next? Only incremental changes are expected from now on.

Install

npm install --save-dev @babel/preset-stage-2

Usage

Via `.babelrc` (Recommended)

.babelrc

{
  "presets": ["@babel/stage-2"]
}

Via CLI

babel script.js --presets @babel/stage-2

Via Node API

require("@babel/core").transform("code", {
  presets: ["@babel/stage-2"]
});

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.

References

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

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