ES2015 block scoping transform

Compile ES2015 block scoping (const and let) to ES5


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



Without options:

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

With options:

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


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.