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  • License MIT

Compile ES2015 block scoping (const and let) to ES5

Package Exports

  • babel-plugin-transform-es2015-block-scoping
  • babel-plugin-transform-es2015-block-scoping/package

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (babel-plugin-transform-es2015-block-scoping) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

babel-plugin-transform-es2015-block-scoping

Compile ES2015 block scoping (const and let) to ES5

Examples

In

{
  let a = 3
}

let a = 3

Out

{
  var _a = 3;
}

var a = 3;

Installation

npm install --save-dev babel-plugin-transform-es2015-block-scoping

Usage

.babelrc

Without options:

{
  "plugins": ["transform-es2015-block-scoping"]
}

With options:

{
  "plugins": [
    ["transform-es2015-block-scoping", {
      "throwIfClosureRequired": true
    }]
  ]
}

Via CLI

babel --plugins transform-es2015-block-scoping script.js

Via Node API

require("babel-core").transform("code", {
  plugins: ["transform-es2015-block-scoping"]
});

Options throwIfClosureRequired

In cases such as the following it's impossible to rewrite let/const without adding an additional function and closure while transforming:

for (let i = 0; i < 5; i++) {
  setTimeout(() => console.log(i), 1);
}

In extremely performance-sensitive code, this can be undesirable. If "throwIfClosureRequired": true is set, Babel throws when transforming these patterns instead of automatically adding an additional function.